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Saint Augustine
Just War in the 21st Century
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Article Index
Just War in the 21st Century
Old Testament and War
Jesus and the New Testament
The Just War: Augustine
The Just War: Aquinas
War in the 21st Century
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Christianity, the West and Just War in the Twenty-First Century

by Peter Lee, Ph.D., King’s College London, Lecturer in Air Power Studies at Royal Air Force College Cranwell in Lincolnshire, United Kingdom

This treatise was first published in Air Power Review, Volume 13, Number 3, Autumn/Winter 2010, pp. 65-84. This version contains several paragraphs that have been expanded from the originally published version. Air Power Review is a publication of the Royal Air Force College, Cranwell, Linconshire, United Kingdom. Reprinted with permission. The website address for Air Power Review is:

The past two decades have witnessed a number of military interventions by US, UK and other allied forces in theatres as diverse as Kuwait, the Balkan region of Europe, Iraq and Afghanistan. At different times over this period President Bill Clinton, President George W. Bush and Prime Minister Tony Blair have made recourse to the vocabulary of just war in a bid to convince their respective peoples to support the deployment of military hardware and personnel in pursuit of political ends. Just war is characterised by a number of criteria that have been codified and embedded in Western war discourse over many centuries and are understood and spoken of beyond the abodes of the powerful and the planning rooms of the armed forces: just cause, right intention, last resort, legitimate authority, proportionality, discrimination of combatants and so on. This article explores early Christian influences on the just war tradition before discussing how the ongoing relevance of secularised versions of these ancient ideas is influencing why and how war is fought in the twenty-first century.

On 12 August 1880, in a speech at Columbus, Ohio, General William Tecumseh Sherman captured the essence of humankind’s fascination with war: “There is many a boy here today who looks on war as all glory, but boys, it is all hell.” No poet or philosopher – either before or since – has encapsulated in so few words what it means when people or states seek political solutions through the use of military force. We honour the heroes, avert our gaze from the hideously wounded and maimed, and speak, often too glibly, of the sacrifices made on the field of battle. I have never experienced war first-hand: the gut-wrenching, heart-pounding cocktail of fear and exhilaration, tragedy and triumph that leaves its indelible mark on those who have found themselves in the firing line. I have, however, glimpsed the hell that war brings. In 2003 I was a military chaplain and glimpsed that hell in the eyes of a widow as she received the news of her fallen husband, and in the eyes of her children as they struggled to comprehend that daddy would never be coming home. I heard echoes of hell in the wavering voice of a young soldier who refused to believe that his new wife might still love him, having left half an arm in the sands of Iraq. I smelt the rancid stench of hell in the weeping bandages of the wounded whose eyes had been searching for the enemy one moment, only to re-open in the bed of a military hospital in another country.

A number of these soldiers professed some form of religious belief, Christian or otherwise; some were implacably opposed to any notions of God or religion; while others appeared not to care much either way. What united almost everyone I spoke to was a desire to understand whether Prime Minister Tony Blair had been right in sending them to war and whether they had conducted themselves properly or let down their comrades. When discussing the justification of the 2003 Iraq invasion or the conduct of individuals involved, the soldiers with whom I dealt, who had little or no philosophical schooling, instinctively resorted to ideas that have been associated with just war for many centuries. They asked questions and made statements like: Did we go in for a good reason? I still think we went for the oil! We should have waited. I don’t know why we’re here – it doesn’t make sense. My CO said we had to go in and that’s good enough for me! In these and other comments ancient just war criteria were the subject of debate once more, criteria that include just cause, right intention, last resort, legitimate authority, proportionality and discrimination of combatants. Not once did the notion of religious war surface, yet the terms in which war was discussed has ancient roots in Christian thought.

This article will provide an overview of some early Christian ideas on just war and their subsequent codification, before going on to consider the ongoing relevance of these ancient concepts, for Christians and non-Christians, in examining why and how war is fought in the twenty-first century. The types of war fought by UK and allied military forces over the past two decades, and the reasons for fighting them, have been different to many of those wars fought in the twentieth century: the two World Wars, the Falklands War and even the Gulf War against Iraq in 1991. Struggle for national survival and defence of sovereign territory has been replaced recently by counter-insurgency wars far from home in Afghanistan and Iraq. These campaigns have been promoted by the British government as a means of improving the security of the UK, whilst at the same time threats from international terrorist organisations against the UK have increased—with those threatening the UK blaming British military involvement in Muslim lands as a primary motivation.

In order to assess the place of just war in today’s rapidly changing global security context, the remainder of this article will take the following shape. The first section will look at the place of war and soldiering in the Bible, drawing attention to some practices that might still be relevant today and other practices of war – particularly from the Old Testament – that should not only be abandoned but opposed. The second section will consider some ideas of the great theologians Augustine and Aquinas concerning the Christian and war, showing how aspects of the just war tradition came to be codified in a way that is still recognisable in its secular form today. The final section will address the relevance of these ancient just war ideas in the current national and global security environment by analysing Prime Minister Blair’s justification of military intervention and the challenges facing those engaged in battle in Afghanistan. Not only will key ideas from both the Bible and great Christian thinkers of the past be applied to contemporary challenges, the limitations of some of these ideas will also be pointed out, based on differences between past and present in the secularisation of just war and the way that the international political system is structured.

The Old Testament and War
War is one of the most ancient of all human activities, with depictions of battle being found in sources as diverse as early cave paintings, stone carvings and the tombs of Egyptian Pharaohs. To that list can be added the Old Testament: the books that Jesus would have studied in scroll form throughout his life. He would have been very familiar with the history of Israel, built as it was on many occasions at the point of a sword. Such was the emphasis on the great battles and warrior kings of Israelite/Jewish history that the long-awaited Messiah was expected by many Jews of Jesus' day to be some kind of freedom-fighter who would use force to set them free from the yoke of Roman domination.

Many of the wars recorded in the Old Testament, even those commanded by God, do not always provide the modern Christian, or anyone else, with the most helpful inspiration for service in the armed forces. Take, as an example, Joshua and the battle for Jericho. After the death of Moses, God commanded Joshua to take the Israelites across the Jordan River to the land that God was going to give them: ‘territory [that] will extend from the desert to Lebanon, and from the great river, the Euphrates – all the Hittite country – to the great sea on the West’.1 The battle of Jericho is recalled in a song that was originally a Negro Spiritual sung by enslaved black Christians; a song that is still sung by children in Sunday school and regular school assemblies as a way of recalling the suffering caused by slavery, as well as the ancient battle. The song includes the words:
Up to the walls of Jericho
He marched with spear in hand;
Go blow them ram horns, Joshua cried
'Cause the battle is in my hands.

Then the lamb ram sheep horns began to blow,
The trumpets began to sound;
Old Joshua shouted glory
And the walls came tumblin' down.

Contrast this romanticised taking of Jericho with a few blasts of ram horn and trumpet with the events recorded in the book of Joshua:

About forty thousand armed for battle crossed over [the river Jordan] before the Lord to the plains of Jericho for war ... Then the Lord said to Joshua, “See, I have delivered Jericho into your hands, along with its king and its fighting men.” ... so every man charged straight in, and they took the city. They devoted the city to the Lord and destroyed with the sword everything living in it – men and women, young and old, cattle, sheep and donkeys.2
No matter how strong an attachment Christians today may have to their spiritual forebears at Jericho, the actions of Joshua’s army would now be described as genocide or ethnic cleansing: exactly the kind of activity that UK and NATO forces opposed in Kosovo in 1999. Even more mystifying, the mass killing of the people of Jericho – whilst following God’s instructions – happened after God had provided Moses with the Ten Commandments: including, ‘Thou shalt not kill’.3 The meaning of this seemingly obvious commandment, sometimes translated as ‘You shall not murder’4, clearly did not extend to killing in the course of battle authorised by God. Yet if any army conducted an attack like Joshua’s on Jericho today, its Commanding Officer would be probably be regarded as insane and those involved would – should – find themselves liable for prosecution at the International Criminal Court.

As well as capturing numerous examples of this kind of battle5 the Old Testament also points to a future that is less bloody and more optimistic – though we may have to wait a while before it arrives. Isaiah writes: ‘In the last days ... Nation will not take up sword against nation, nor will they train for war any more’.6 The difficulty for the Christian today is that these last days marked by peace and tranquillity appear no closer today than they would have appeared to the Israelites more than two thousand years ago. For the non-Christian who does not recognise either the authority of the Bible or the God that it represents, these words read as little more than wishful thinking.

A more accurate description of the circumstances in which we live, a description that would be recognised by most people regardless of their views on faith or religion, can be found in the poetic words of Ecclesiastes: ‘There is a time for everything ... a time to kill and a time to heal ... a time for war and a time for peace’.7 These can be read as simple statements of fact, unlike the prophetic words of Isaiah that require a dimension of personal faith or belief if they are to hold meaning in the present: ‘For to us a child is born, to us a son is given, and the government will be on his shoulders. And he will be called Wonderful Counsellor, Mighty God, Everlasting Father, Prince of Peace’.8 The promised Messiah would be a Prince of Peace whose function would be to usher in God’s kingdom on earth: at which point nations would stop taking up arms against other nations.

Christians therefore find themselves in a far-from-perfect in-between place, believing that the kingdom of God has been promised in the Old Testament and subsequently inaugurated on Earth by Jesus. However, the perpetual peace that has been promised will not be finalised until some unspecified point in the future: the last days. In this in-between place in which we live, tyrants still inflict suffering on the innocent; nation still makes war on nation; and numerous groups resort to indiscriminate violence as a means of influencing the political process and furthering aims that can be driven by ideology, religion, or social and economic marginalisation. What then are the implications for, and responsibilities of, the person who would take up arms in defence of his or her country or the vulnerable citizens of the world? To begin to address some of the issues raised by this question let us turn to the New Testament and the words of Jesus himself.

Jesus and the New Testament
The first difficulty anyone faces when turning to the words of Jesus in the gospels as a source of guidance on war in the twenty-first century is that he did not even offer guidance on war in his own century. Isaiah had prophesied that the Messiah would come as a Prince of Peace, but when Jesus commenced his public ministry, as recorded in Luke’s gospel, it was not the words of Isaiah 2:4 that he claimed to fulfil but another, later prophecy recorded in Isaiah:

“The Spirit of the Lord is on me, because he has anointed me to preach good news to the poor. He has sent me to proclaim freedom for the prisoners and recovery of sight for the blind, to release the oppressed, to proclaim the year of the Lord’s favour ... Today this scripture is fulfilled in your hearing.”9

Given that the land of Israel was occupied by a foreign power and controlled by the Roman Army, if ever there was a time for Jesus to provide clear instructions on participation in war, or the rejection of participation in war, this was it. The priority, instead, was to proclaim the year of the Lord’s favour and declare: “The kingdom of God is near.”10 As part of his bringing in of the kingdom of God, Jesus emphasised non-violence on a number of occasions. For example, he said: “Do not resist an evil person. If someone strikes you on the right cheek, turn to him the other also.”11 Again, like the Ten Commandments, there is an elegance about these words. However, like the brutal wars instituted by God after he gave his people the Ten Commandments to follow, things are not as straight forward as they seem. For example, in advocating that resistance should not be offered to evil people and the other cheek turned instead, Jesus refers to individual actions and not to the assembled ranks of soldiers on the field of battle. Should an individual turn the other cheek when faced with the sword of a good and honourable soldier on the battlefield? Such an ethical choice appears to fall outside of the constraints set out by Jesus.

There are have always been a number of Christians who have held the view that the path of non-violence is the only ethical way to live and who would not defend themselves, or others, with force when faced by personal attack or a rampaging enemy. Supporting this view is another example of Jesus encouraging a non-violent attitude; this time towards the end of his life as he was being arrested in the Garden of Gethsemane in the build-up to his crucifixion:

Then the men stepped forward, seized Jesus and arrested him. With that, one of Jesus’ companions reached for his sword, drew it out and struck the servant of the high priest, cutting off his ear. “Put your sword back in its place,” Jesus said to him, “for all who draw the sword will die by the sword.”12

The first thing to note is that the crowd that came for Jesus did not represent the civil (that is, Roman) authorities: it was sent by the ‘chief priests and the elders of the people’13, and the members of the crowd had armed themselves with swords and clubs. No one in this dispute had any right to take up arms, neither the individuals seizing Jesus nor the person who sought to protect him.14 Contrast Jesus’ stern rebuke of the companion who tried to defend him with a sword with Jesus’ attitude towards the centurion who came to him on another occasion seeking healing for his servant. Jesus said to the centurion: “I have not found anyone in Israel with such great faith ... Go! It will be done just as you believed it would.”15 Jesus had called many of his disciples to leave their previous careers and livelihoods to follow him,16 and he had also called others to give up lifestyles that did not conform to the requirements of the kingdom of God.17 Yet Jesus’ encounter with the centurion resulted in only praise for the soldier’s great faith and no instruction to hang up his sword or seek a new non-violent career.

The basis of the disparity in Jesus’ response to the companion who defended him with the sword and the centurion who wielded the sword professionally is found in his attitude to the authorities (civil authorities, not religious authorities). Jesus – who on one occasion took a whip and violently drove out traders and money-changers who were desecrating the temple in Jerusalem – instructed that taxes should be paid to the authorities, saying, “Give to Caesar what is Caesar’s, and give to God what is God’s.”18 The centurion bore his sword as a soldier whose authority to do so was granted by Caesar himself. The individual rebuked by Jesus had no such right to wield a sword. Jesus’ attitude to the legitimate and illegitimate bearing of arms is reinforced later in the New Testament by the apostle Paul, who also wrote about the Christian’s responsibility to the authorities: ‘Everyone must submit himself to the governing authorities, for there is no authority except that which God has established’.19

The linking of authority and legitimacy concerning the bearing of arms is crucial, not only to Jesus and Paul in a Christian context but to those who would take up arms on behalf of their states today. Furthermore, since the time of Jesus the issue of legitimacy and authority has been central to debate surrounding when, and how, a Christian should serve as a soldier: in what we now know as the just war tradition. It is to some of the key writers and ideas in the just war tradition that we now turn.


The Just War: Augustine
In the fourth century worship of the Christian God replaced the traditional worship of Roman gods as Christianity became the official religion of the Roman Empire. This prompted one practical difficulty for the Roman emperors and those in authority: how to maintain the might of the Roman Army, upon which the security of the Empire depended, when many Christians would not, or felt they could not, serve. In the centuries since Jesus lived and died the Roman army had been used on a number of occasions as a tool with which to persecute Christians. Even Christians who served as soldiers had been persecuted. Perhaps not surprisingly, the legacy of this abuse was reluctance on the part of many Christians to serve in the army. In addition, some of the early Church Fathers emphasised the aspects of Jesus teaching that promoted non-violence (‘turn the other cheek’ and ‘put your sword back in its place’ already mentioned above), and many early Christians supported their views. Matters were complicated even further when, in 410, Alaric and his army of Visigoths sacked Rome: resulting in criticism by many citizens of the Christian God’s ability to protect Rome as the traditional gods had in the past. In this complex political, military and cultural environment, Augustine – Catholic Bishop of Hippo and theologian – defended Christianity against charges that God was failing to protect Rome and her people, as well as addressing the issue of whether or not Christians could serve in the army.

In his book City of God Augustine addressed the challenge to God’s authority by those who accused God of being unable to protect the city and people of Rome. Based on a biblical understanding of the kingdom of God, as well as Jesus’ statement that his followers ‘are not of the world, even as I am not of it.’20 Augustine described the two cities that define human existence: the Earthly City and the City of God. These refer to an earthly, physical existence and an eternal life with God. He also set out how citizenship or membership of either city was to be determined: 'I classify the human race into two branches: the one consists of those who live by human standards, the other of those who live according to God's will'.21 The priority for the Christian was to seek to belong to the City of God through both faith and good action, while those who did not know God, or rejected him, belonged to the Earthly City. Christians were therefore not to worry unduly about the city of Rome but instead focus on the City of God, the place where they, through faith, would ultimately reside with God for all eternity.

Possibly the most important of Augustine’s ideas for Christians in both the fifth and twenty-first centuries, and for anyone else who would serve in the military today, is his argument that there is such a thing as a just war. The purpose of a just war, as opposed to an aggressive war fuelled by greed or ambition, is the pursuit of a better state of peace: ‘Peace is not sought in order to provoke war, but war is waged in order to attain peace’.22 Such wars are fought against tyrants or other power-hungry rulers that would threaten their neighbours:

The desire for harming, the cruelty of revenge, the restless and implacable mind, the savageness of revolting, the lust for dominating, and similar things – these are what are justly blamed in wars. Often, so that such things might also be justly punished, certain wars that must be waged against the violence of those resisting are commanded by God or some other legitimate ruler and are undertaken by the good.23

According to Augustine, the pursuit of a better state of peace must therefore be for a good cause – such as overcoming the ruler who has demonstrated a savage lust for domination and a desire to harm others – and must be authorised either by God or a legitimate, and good, ruler. We can also see here the beginnings of an influential distinction Augustine makes in separating the moral responsibility of the king or ruler who takes a nation or empire to war from the responsibility of the soldiers who fight those wars. Of the moral responsibility of soldiers Augustine wrote:

Therefore, a just man, if he should happen to serve as a soldier under a human king who is sacrilegious, could rightly wage war at the king's command, maintaining the order of civic peace, for what he is commanded to do is not contrary to the sure precepts of God ... perhaps the iniquity of giving the orders will make the king guilty while the rank of servant in the civil order will show the soldier to be innocent.24

There are two aspects to Augustine’s argument about the moral responsibilities of the soldier. Firstly, Augustine was not primarily concerned with war per se, he was concerned with producing good Christians who would spend eternity with God and whose conduct on earth should reflect the values of God’s kingdom on earth. Therefore, as a general principle, individuals could only be held morally accountable, before God, for actions that they are directly and individually responsible for undertaking. Since the soldier has no say, and this remains as much the case today as it was 1600 years ago, in whether or not a war will be undertaken (because that decision is taken by the ruler or sovereign) the soldier cannot be held morally accountable for the decision. It is only for actions on the field of battle that the soldier will be judged by God. In the quote from Augustine here he goes further: even if the decision to go to war is wrong and taken by a sacrilegious king, the soldier remains morally innocent because he has upheld God’s civic order. This part of Augustine’s argument is based on Paul’s command in his letter to the Romans mentioned above: ‘Everyone must submit himself to the governing authorities, for there is no authority except that which God has established’.25 While the modern political structure of the UK bears little resemblance to that of the Roman Empire in the fifth century, the idea of submitting to the authorities is one that is still relevant to all soldiers.

The United Kingdom’s armed forces do the bidding of the civil authorities: the elected government of the day. In turn, junior ranks submit to the authority of senior ranks. Submitting to authorities is not merely an ancient, Christian, irrelevant notion; it is set out very clearly in the Queen’s Regulations for the three Services—as are the punishments to be handed down for breaches such as desertion or insubordination or refusing to carry out a legal order. No matter how strongly a serviceman or servicewoman feels about some act of violent injustice, either in his or her own country or elsewhere, such individuals have no right to take up arms and intervene under their own volition.

We should not think that Augustine happily tolerated those who made bad, or immoral, decisions to go to war. He was as concerned for the soul of the ruler as he was for everyone else’s soul. On making the decision to go to war he writes: ‘But the wise man, they say, will wage just wars. Surely, if he remembers that he is a human being, he will lament that fact that he is faced with the necessity of waging just wars; for if they were not just, he would not have to engage in them’.26 Central to Augustine’s concept of the just war, an idea that remains as important to just war thinking today as it has in every century since, is the idea that a war should only be pursued for a just cause: the most important of which is defence of which Augustine calls ‘the common well-being’27, or what we might refer to today as defence of the realm or national self-defence. He wrote:

…it makes a great difference by which causes and under which authorities men undertake the wars that must be waged. The natural order, which is suited to the peace of mortal things, requires that the authority and deliberation for undertaking war be under the control of a leader, and also that, in the executing of military commands, soldiers serve peace and the common well-being.28

The most important of Augustine’s ideas on the just war, which were largely unstructured and scattered throughout his extensive writings, were later taken, added to, and presented in a much more concise and coherent structure by Thomas Aquinas in the thirteenth century.


The Just War: Aquinas
Aquinas, like Augustine, was both a monk and a priest whose chief concern was for Christians to live in a way that would honour God on earth and lead to an eternity with God in heaven. He wrote extensively on how Christians should live and conduct themselves, addressing a vast array of issues—from Christian doctrine to individual moral conduct. In his writings, Aquinas brought together ideas from a huge number of sources, the most important Christian influence being Augustine and his most important philosophical influence being the Greek philosopher Aristotle: both of whom had written on the notion of the just war. It is worth noting that Aquinas was only able to incorporate Aristotle in his writings because the works of Aristotle had been preserved by scholars in the Middle-East and translated and brought to Europe during the Crusades. Having weighed up the key arguments of the theologians and philosophers who had come before him, Aquinas succinctly codified the conditions to be satisfied for a war to be considered just:

In order for a war to be just, three things are necessary. First, the authority of the sovereign by whose command the war is to be waged ... Secondly, a just cause is required, namely that those who are attacked, should be attacked because they deserve it on account of some fault ... Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil.29

The just war criteria that Aquinas set out – legitimate authority, just cause and right intention – are still at the heart of just war debate in the twenty-first century. However, there are some important differences to be taken into account. One of the differences between Aquinas’ time and the present is the relationship between political authorities and religious authorities. Aquinas wrote: ‘The secular power is subject to the spiritual, even as the body is subject to the soul’.30 It was important to him that war should be authorised and commanded by the sovereign (and thus being granted legitimacy) as well as being fought for a just cause. The sovereigns in Europe at that time were usually kings and princes who owed their religious allegiance to the Pope and the Catholic Church, and one of Aquinas’ reasons for trying to limit when wars could take place was to preserve the life of Christians who would therefore meet in battle. In contrast, there are few sovereigns in the modern world who could authorise war in the way that Aquinas described, and even fewer, if any, who would submit to religious authority.

With regard to Aquinas’ second criteria, just cause, in the current international system it is the responsibility of the United Nations (UN), and in particular the UN Security Council, to assess the causes of war and decide whether or not a particular war is legitimate or justified. In addition, individual states retain the sovereign right to self defence: ‘Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations’.31 When the Charter was written and signed by the victorious Allied Powers towards the end of World War II, limits were placed on that right to self-defence, with ultimate responsibility reverting to the Security Council: ‘The Security Council shall determine the existence of any threat to the peace, breach of the peace, or act of aggression and shall make recommendations, or decide what measures shall be taken … to maintain or restore international peace and security’.32 However, what could not have been foreseen as the UN Charter was drawn up was the subsequent rapid degeneration of relationships between the major powers as the Cold War emerged and permanent members of the Security Council33 began to use their veto powers to pursue vested political interests and to frustrate their political rivals. 

The UN has no enforcement powers or political sovereignty of its own through which it can enforce its will on intransigent nations or non-compliant actors, such as Iraq and Saddam Hussein.  When the UN Charter was written prior to the end of World War II, the Allied Powers had millions of men under arms in their various armies, navies and air forces and the text itself suggests that the Security Council would be able to enforce its will: ‘[The Security Council] … may take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security’.34 The political reality today is that the kind of action suggested here is all but impossible.  The ultimate testimony to the ineffectiveness of the UN and the Security Council to enforce peace and stability is found in the killing fields of Cambodia and Rwanda.  The third of Aquinas’ criteria for a just war, right intention, is very difficult to assess in the current state-centric international system. With so many competing interests it is difficult in most political settings to determine the intentions of the actors involved. The UN Security Council is limited in its ability to determine whether a particular war is just or not by the multiple layers of motivations that underpin the intentions of any state that sets out to engage militarily with another, even a defensive war.

Aquinas’ emphasis on right intention also has implications for soldiers who fight in battle. He took the biblical view that killing is wrong but, like Augustine, made an exception when it came to the soldier taking life in battle. Not only was killing in war acceptable for Aquinas, in the right circumstances it was positively the ethical thing to do. He wrote: ‘The common good of many is more Godlike than the good of an individual. Wherefore it is a virtuous action for a man to endanger even his own life, either for the spiritual or for the temporal common good of his country’.35 In other words, the soldier who endangers his own life, or who takes the life of another in battle, is carrying out a virtuous act: as long as the killing is for the common good, such as defence of the soldier’s country or those who cannot defend themselves. Even then, killing in battle is only justified if it is absolutely necessary. The soldier must be committed to upholding the common good by winning in battle. If the soldier’s intention is to kill as many people as possible, regardless of whether they are combatants engaged in the war or simply innocent bystanders, then that individual should be subject not only to God’s eternal punishment but to legal punishment on earth as well. Aquinas’ words on the use of force are relevant to both soldiers and civilians today:

Wherefore if a man, in self-defense, uses more than necessary violence, it will be unlawful: whereas if he repel force with moderation his defense will be lawful, because according to the jurists ... "it is lawful to repel force by force, provided one does not exceed the limits of a blameless defense."36

Soldiers on the field of battle today will be held legally accountable if they exceed the level of force authorised in their Rules of Engagement. Few will care about Aquinas’ notion of divine punishment, but in the case of a war crime being committed an individual could be prosecuted at the International Criminal Court. British soldiers have stood trial in British courts in recent years as a result of illegal actions in the face of the enemy in Iraq, such as the beating and even killing of prisoners. In the centuries since Aquinas wrote about just war, many other great thinkers have contributed to this tradition of thought. In recent centuries increasing emphasis has been placed on the conduct of soldiers in war and the two just war terms that guide such conduct, legally as well as ethically, are discrimination and proportionality. Discrimination, in the just war sense, stresses the importance of targeting only legitimate combatants and avoiding the killing of civilians or noncombatants. This idea is captured in the Geneva Conventions37, non-religious international humanitarian law to which the UK is a signatory, as well as individual combatants’ Rules of Engagement. A noncombatant is anyone not legitimately engaged in war. So, for example, once a soldier has been taken as a prisoner of war he or she is no longer a combatant. Similarly, a wounded enemy soldier who is disarmed and taken to hospital for treatment is a noncombatant. Yet it is clear that the kind of interventionist war being fought in Afghanistan, like the recent war in Iraq, is not between two armies whose soldiers are clearly identifiable as such.

The final section of this article will examine some of the particular ethical challenges surrounding war in the twenty-first century by exploring Tony Blair’s justification of the 2003 Iraq invasion, before going on to examine the ethical implications for combatants fighting against a highly motivated insurgent enemy. What becomes apparent is that while some of the philosophical underpinnings of just war remain in political and military discourse in the West (such as the pursuit of justice and the prevention of unnecessary death or suffering), the theological motivations that helped shape the tradition over many centuries are no longer applied and state policies are not dictated by a desire to enter the Christian’s heaven.

War in the Twenty-first Century
To begin to understand Blair’s justification of Iraq in 2003 it is necessary to comprehend the moral implications of the almost aggressive internationalism he advocated at the conclusion of the twentieth century. In April 1999, as NATO bombarded Yugoslavia with the intention of forcing Slobodan Milosevic to stop his soldiers’ attacks on Albanian Kosovars, Blair set out his internationalist credentials:

Globalisation has transformed our economies and our working practices. But globalisation is not just economic. It is also a political and security phenomenon. We live in a world where isolationism has ceased to have a reason to exist. By necessity we have to co-operate with each other across nations ... We are all internationalists now, whether we like it or not.38

Blair did not simply want to increase global trade or cultural exchanges and he did not seek to expand migration or make travel across borders easier. He sought to expand the concepts of globalisation and internationalism to include the strengthening or reforming of international institutions so that the rights of oppressed peoples could be protected: by force where necessary. He continued:

Many of our domestic problems are caused on the other side of the world...These problems can only be addressed by international co-operation ... We cannot turn our backs on conflicts and the violation of human rights within other countries if we want still to be secure ... We need new rules for international co-operation and new ways of organising our international institutions.

Blair’s internationalism was presented in terms that prioritised the protection and even enforcement of individual human rights. On one level he could be commended for adopting an ethical position that prioritises concern for the vulnerable and downtrodden of the world. Such an attitude reflects the biblical injunction: ‘Love your neighbour’.40 During his time as Prime Minister Blair’s advisors sought to play down any impact his Christian beliefs may have had on his decision making for fear of causing outrage or offence. Yet throughout his tenure he worshipped in church regularly and was attended regularly by a personal chaplain. Shortly after his resignation as Prime Minister he converted to Roman Catholicism. More recently Blair acknowledged: ‘I believe, as someone of Faith, that religious faith has a great role to play in an individual's life.’41 Despite this, he probably did not invoke internationalism as an expression of his own religious belief and practice but he did draw upon a moral discourse – the responsibility for the strong to look out for the weak and vulnerable – that has ancient Christian connections and general acceptance in secular society. The difficulty of adopting such an approach is that it contradicted the rights of states to exist free from external interference: rights which, according to international law enshrined in the Charter of the United Nations, should be considered inviolate.42

Despite the constraints set out in international law, Blair suggested new rules that could govern intervention in other states:

So how do we decide when and whether to intervene. I think we need to bear in mind five major considerations: First, are we sure of our case? … Second, have we exhausted all diplomatic options? ...Third, on the basis of a practical assessment of the situation, are there military operations we can sensibly and prudently undertake? Fourth, are we prepared for the long term? ... And finally, do we have national interests involved?43

The five criteria for military intervention that Blair set out correspond remarkably with the jus ad bellum criteria that had characterised the just war tradition for centuries: just cause, last resort, reasonable chance of success, proportionality and right intention.44 However, no matter how commendable or otherwise Blair’s internationalist aspirations were, he could only achieve his aims if he ignored, changed or somehow circumvented international law. This, in turn, posed a significant dilemma for Blair when it came to justifying the UK’s involvement in the 2003 Iraq invasion.

One of the reasons the US/UK-led invasion of Iraq in 2003 caused so much controversy around the world is that it was not explicitly authorised by the UN Security Council. It was not authorised because three permanent members of Security Council, and some others, were not satisfied that there was sufficient cause to justify such action at the time it was taken: the only legal basis for war in the UN Charter being national self-defence. Saddam Hussein had failed to comply with numerous UN Security Council resolutions over many years and he was not co-operating with UN weapons inspectors. However, it could not be shown conclusively (and events subsequently proved opponents of the invasion correct) that he posed a significant threat to the UK, the US or even his neighbours.

In addition, many people remained unconvinced that the intentions of the UK and US matched up to what was being said in public by senior government officials. The publicly stated intentions of the UK and US leadership included the following: to rid Iraq of weapons of mass destruction (WMD) and make the world safer; regime change; getting rid of Saddam Hussein; promoting democracy in Iraq; and keeping the people of Iraq safe from Saddam’s brutality. Even granting that Blair and Bush were genuine in their concern for oppressed Iraqis in 2002/3, neither they nor previous administrations in the UK or US had shown the same degree of concern in 1988 when the worst of the atrocities took place: the chemical bombing of Iraqi Kurds in Halabja. Adding to the complexity of the issue of intention was Iraq’s location above one of the biggest oil deposits in the world. As a result the accusation of ulterior motives was, and still is, levelled against the Americans, the British and their allies.

Although Blair used ancient and widely accepted Western just war ideas in his proposed new interventionism in 1999, the world by and large remained sceptical. Despite his apparently well-intentioned plea and the seemingly sound moral arguments that it was based upon, other Western states failed to rally behind him. In addition, in many non-Western states Blair’s ideas were interpreted as a new form of Imperialism. This scepticism was subsequently borne out in relation to Iraq when Blair failed to satisfy a number of the conditions he himself had proposed in 1999:

First, are we sure of our case? … Second, have we exhausted all diplomatic options? ...Third, on the basis of a practical assessment of the situation, are there military operations we can sensibly and prudently undertake? Fourth, are we prepared for the long term? ... And finally, do we have national interests involved?45

Had Blair followed his own guidelines here for military intervention he would have had to either cancel or postpone the UK’s involvement in the March 2003 invasion. Regardless of the outcome of the ongoing Chilcot Inquiry into the 2003 Iraq War, history is unlikely to be kind to Blair. This will not be a consequence of the failure of just war ideas in the twenty-first century: it will be a consequence of Blair’s failure to satisfactorily apply just war principles that he had previously advocated.

Moving on from ad bellum concerns to in bello challenges, the final section of this article now examines some of the ethical difficulties facing US, UK and other NATO combatants in their long campaign against a highly motivated insurgent enemy in Afghanistan. Alongside Iraq, the war in Afghanistan has defined the early years of the twenty-first century for the British and allied armed forces. UK forces entered Afghanistan as part of a collective NATO response to the attacks on the United States in September 2001. These attacks, in turn, were planned by Al-Qaeda cells that had been allowed to freely operate training camps by the Taliban regime at that time, at least partly motivated by an extreme, anti-Western version of Islam.

Militarily, the might of the US, UK and other NATO forces that entered Afghanistan in 2001/2 was overwhelming. As with the subsequent invasion of Iraq, the conventional war was won in a matter of weeks. In both Iraq and Afghanistan short, sharp conventional wars gave way to lengthy counter-insurgency wars against highly motivated enemies who were, and are, determined to remove what they see as occupying powers from their lands. All of the military advantages provided by aerial reconnaissance, precision guided missiles and other high-powered airborne weapons, tanks and heavy armour, count for very little against an enemy that is hard to find and expert at laying well hidden and highly effective roadside bombs. In Afghanistan, more than 1800 coalition military personnel have been killed to date, with numbers continuing to rise. Complicating the matter further for the allied combatant in 2010 is the uncertain nature of the mission in Afghanistan. If the initial invasion was a reaction to the 9/11 attacks on the US and a denial of training grounds to Al-Qaeda, recent reasons given by the UK and US governments for continued engagement in Afghanistan include: support of a fledgling democracy; making Europe safe from terrorist attack; promotion of human rights, especially for women and girls; reduction of the export of heroin; and advancement of regional stability. In the midst of this political uncertainty members of the British armed forces are asked to expose themselves to considerable risk.

So what is the relevance, if any, of just war principles to British combatants serving in a campaign that looks increasingly unwinnable, against the backdrop of public opinion that is increasingly opposed to their ongoing involvement and a government whose support appears fragile, time-limited and cash poor? The first answer to this question can be found in the written guidance on the law of armed conflict that is issued to every combatant:

All personnel must be aware of the basic rules of the law of armed conflict, including the practical application of the principles of military necessity, proportionality, distinction and humanity ... [And] Comply with the law of armed conflict and with Service law.46

These instructions provide explicit guidance on how combatants emerge as just in the conduct of war: ‘Comply with the law of armed conflict’.47 Such legal requirements include the responsibilities of combatants set out in the Geneva Conventions to which the UK is a signatory. I want to consider two aspects of this instruction: the means by which such compliance is achieved and the just war discourses that this instruction draws upon. The Geneva Conventions stipulate that combatants should be taught the law of armed conflict as part of the requirements of international humanitarian law. Conformity to the Geneva Conventions should, according to the guidance provided by the International Committee of the Red Cross, be enforced through military instruction based on military manuals and informed by ‘military pedagogy’: ‘in exactly the same way as the preparation for combat’.48 A number of supplementary instructional methods are specified: ‘lectures, films, slides, audio-visual methods, war games including questions and answers etc’.49 The British armed forces, like many others around the world, use such techniques to ensure that their combatants are familiar with the law and know how to act in conformity to it. As a result, the soldier emerges as just through adherence to the law, reinforced by disciplined repetition and training.

The aspects of law with which combatants must be concerned include: ‘the practical application of the principles of military necessity, proportionality, distinction and humanity’.50 These principles can all be found in the just war tradition and their meanings have remained reasonably stable over the centuries. However, closer examination of one of these factors will be sufficient to show how the ideas that underpin just war have changed. Take, for example, ‘military necessity’. For Augustine, 1600 years ago, the just warrior would only carry out such actions on the battlefield as are required by ‘stern necessity'.51 However, it is not the execution of ‘necessary’ actions in war that constituted Augustine’s soldier as ethical. Augustine’s primary concern was for the soul of the Christian, in this context the soldier. He encouraged the Christian to live a good life on earth with the aim of achieving eternal life in the heavenly City of God. In contrast, British Rules of Engagement no longer have a religious basis: they are based on the requirements of secular law. While modern notions of necessity, proportionality, distinction and humanity owe their heritage to Christian just war writers over the centuries in the West, their current framework is non-religious and law oriented.

It is easy to demand that combatants exercise proportionality and discrimination when they are engaged in war fighting, but the nature of war so far in the twenty-first century has made this increasingly difficult. In Afghanistan, like Iraq, it is almost impossible to tell friend or foe because of a lack of military uniforms. The insurgents are civilians, members of Afghan society, and they launch attacks on NATO forces from amongst their fellow civilians. Yet soldiers are still required to distinguish between legitimate targets and innocent bystanders. Furthermore, such tactics by Taliban or Al-Qaeda fighters can only be successful if UK and other NATO personnel are restrained in their responses and not indiscriminate in reprisal attacks. Those who choose to delay, even slightly, before returning fire, dropping a bomb or launching a missile, in order to protect the innocent, may well increase the risk to themselves. However, that is what just war and international humanitarian law demands: combatants should accept additional risk to reduce the danger to non-combatants. It is notable that when Gen. McCrystal assumed command of the International Security Assistance Force in Afghanistan in 2009 he made it a strategic priority to reduce the number of Afghan civilians killed as ‘collateral damage’ as part of the ‘hearts-and-minds’ campaign, a principle reinforced by his successor, Gen. Petraeus.

As a result of the tactics adopted by the Taliban and Al-Qaeda some would argue that ‘the gloves need to come off’, suggesting that increased aggression and less discrimination by NATO forces would be more militarily effective. On the surface such an approach is appealing, especially for combatants who stand in the firing line and politicians who want quicker results. Such a temptation must be resisted because it would simply ensure a bigger loss for the UK and its allies. The loss would take a number of forms. I suggest that the first loss would be strategic failure, which may still happen anyway. If the UK knowingly unleashes a brutal war fighting machine on the civilians of Afghanistan, some of whom might be Taliban fighters and some not, the remaining fragile support for the campaign by the British public would evaporate. With the UK being a signatory to the International Criminal Court British politicians and military commanders who advocated such an approach would leave themselves open to prosecution. As Carl von Clausewitz, the great Prussian strategic theorist, pointed out two centuries ago in his book On War, the military needs the moral and material support of the people and the political support of the government if it is to successfully engage in war. The International Assistance Force could win every tactical engagement with the Taliban and Al-Qaeda fighters yet still suffer political defeat, paralleling the experience of the Americans in Vietnam. The second loss that the unrestrained use of force would incur would be the loss of British self-identity that for most citizens is characterised by a sense of justice and fair play. For the British people to have to see themselves as deliberate purveyors of indiscriminate destruction would be a demand too far. Finally, any claim that the UK could make to being a force for good, particularly in Afghanistan, would be ridiculed around the world. The long-term consequences for a country that is rich in history but small in size and poor in natural resources could be severe.

The only practical option, therefore, for the UK in making war in the twenty-first century is to engage with just war principles. One consequence of the ongoing doubts about Prime Minister Blair’s justification of the 2003 invasion of Iraq is a sense among the British people that they were somehow misled. If or when the time comes that the present, or a future, Prime Minister believes it to be essential for the UK to go to war again it is likely that the British people will demand a higher burden of proof than might previously have been the case. In the execution of war, especially interventionist wars like Afghanistan, proportionality and discrimination will be essential if support for war is to be maintained and a positive outcome achieved. If the constraints of engaging an enemy in a just manner results in a sense of fighting with one hand tied behind our backs, so be it. This is a price that must be paid if the values that Britons claim to cherish are not to be sacrificed on the altar of military expediency.

Peter Lee served as a Royal Air Force chaplain during the build-up to the 2003 invasion, and for most of the period of the UK’s involvement in Iraq. After hostilities commenced he spent five months at a military hospital in Cyprus providing pastoral support to wounded, maimed and injured soldiers who had been airlifted from the battlefield. During this period Dr Lee developed a keen interest in the way the intervention was justified, particularly by Prime Minister Tony Blair. This prompted extensive reading of the classic just war arguments, eventually leading to formal research in the field at King’s College London War Studies Department. Since 2008 Dr Lee has been employed by King’s College London as a Lecturer in Air Power Studies based at Royal Air Force College Cranwell in Lincolnshire, specialising in the ethics of war. In 2010 he gained his PhD in War Studies for a thesis entitled A Genealogy of the Ethical Subject in the Just War Tradition. Dr Lee is regularly invited to lecture on this subject to military, academic and wider audiences.



1. Joshua 1:4. Unless otherwise stated, all Bible references are taken from the New International Version.
2. Text from Joshua 4:13; 6:2; 6:20,21.
3. Exodus 20:13, King James Version.
4. For example, the New International Version.
5. See also 1 Samuel 15: ‘This is what the Lord Almighty says: “I will punish the Amalekites for what they did to Israel when they waylaid them as they came up from Egypt. Now go, attack the Amalekites and totally destroy everything that belongs to them. Do not spare them; put to death men and women, children and infants, cattle and sheep, camels and donkeys.”’
6. Isaiah 2:4.
7. Ecclesiastes 3:1, 3, 8.
8. Isaiah 9:6.
9. Luke 4: 18-19, 21, quoting Isaiah 61:1,2.
10. This declaration is also found in Mark 1:15 and Luke 10:11, though in Matthew’s gospel Jesus is recorded as referring to the kingdom of heaven, rather than the kingdom of God. A difference usually attributed to the cultural and religious differences in the audiences for which the respective gospels were intended.
11. Matthew 5:39.
12. Matthew 26:50-52.
13. Matthew 26:47.
14. That the crowd had no legitimate authority for their actions is evidenced by what happened after Jesus had been brought before the religious authorities: he had to be taken before the Roman governor Pilate who, alone, could authorise punishment for his alleged crimes.
15. Matthew 8:10, 13.
16. See Matthew 4:18-22; Mark 2:14; John 1: 35-51.
17. The rich young ruler in Matthew 19:16-30, and the Samaritan woman he encountered at the well in John 4:1-26.
18. Matthew 22:21.
19. Romans 13:1.
20. John 17:16.
21. Augustine, City of God, Trans. Henry Bettenson (London: Penguin Classics, 2003) XV.1, p. 595.
22. Augustine, Letter 189 to Bomiface, in Fortin, E.L. and Kries, D. (Eds.) Augustine: Political Writings, Trans. Tkacz, M.W. and Kries, D. (Indianapolis: Hackett, 1994) p. 220.
23. Augustine, Against Faustus the Manichean, Ch. XXII.74, in Fortin, E.L. and Kries, D. (Eds.) Augustine: Political Writings, Trans. Tkacz, M.W. and Kries, D. (Indianapolis: Hackett, 1994) p. 221/2.
24. Augustine, Against Faustus the Manichean, XXII, Ch.74 in Reichberg, G.M., Syse, H. and Begby, E. (Eds) The Ethics of War (Oxford: Blackwell Publishing, 2006) p. 82.
25. Romans 13:1.
26. Augustine, City of God, XIX.7, p. 861/2.
27. Augustine, Against Faustus the Manichean, p. 81.
28. Id.
29. Aquinas, Summa Theologica, II-II, Q. 40, A. 1, p. 1813/14.
30. Ibid., II-II, Q. 60, A. 6, p. 1934.
31. Charter of the United Nations, Chapter 1, Article 51, located at 10 March 2010.
32. Ibid., Chapter VII, Article 39.
33. The five Permanent Members of the UN Security Council, each with Veto powers, are the US, UK, Russia, China and France.
34. Ibid., Chapter VII, Article 41.
35. Aquinas, Summa Theologica, II-II, Q. 31, A. 3, p. 1762.
36. Ibid., Q. 64, A. 7, p. 1961.
37. The full text and history of the Geneva Conventions can be found at, accessed 23 August 2010.
38. Blair, 24 Apr 1999, Speech at the Economic Club, Chicago.
39. Id.
40. Matthew 5:43.
41. Blair, Speech to launch the Faith Foundation, 30 May 2008, from: 10 December 2009.
42. ‘All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.’ Charter of the United Nations, Art. 2, Para. 4, located, 4 December 2008.
43. Blair, op cit.
44. For further explication of just war criteria see Norman, R., Ethics, Killing and War (Cambridge: Cambridge University Press, 1995) p. 118. For similar summaries see Bellamy, A. J., Just Wars: From Cicero to Iraq (Cambridge: Polity Press, 2006) p. 121–3; McMahan, J., 'Just Cause for War', Ethics & International Affairs, Volume 19, No. 3 (Fall 2005) p. 5; or Rengger, N., ‘The Ethics of War: The Just War Tradition’, in Bell, D., (Ed.) Ethics and World Politics (Oxford: Oxford University Press, 2010) pp. 296-298.
45. Blair, 1999, op cit.
46. Aide Memoire on the Law of Armed Conflict, JSP 381, Revised February 2005, Ministry of Defence, located at , Para. 4, accessed 10 January 2009.
47. Id.
48. Programmes of military instruction, Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977. Part 5, Section 1, Article 83, Para. 3376, located at, accessed 15 January 2010.
49. Id.
50. Aide Memoire, op cit.
51. Id.


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Last Updated on Thursday, 17 February 2011 14:46