The Challenge of Moral Certainty in a Just War

This article originally appeared in the Autumn 2026 edition of the Social Issues Bulletin.

“For the one in authority is God’s servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God’s servants, agents of wrath to bring punishment on the wrongdoer.” (Rom. 13:4)

The Christian just-war tradition (CJWT) provides a moral framework to assist in determining when the use of military force is justifiable, as well as the moral conduct of its combatants. Emerging from Christian thinkers such as Augustine and later refined by Aquinas, it has further developed to balance the Christian commitment to peace with the responsibility to protect justice and the innocent. Once war is engaged then conduct – meaning discriminating between combatant and non-combatant, and all military actions being proportionate – must be morally attainable if war is not to degenerate into all-consuming hellishness.

The nineteenth-century military theorist, Carl von Clausewitz, was first to articulate, in a holistic approach, both the nature and character of human conflict. He argued that the fundamental nature of war – the use of violence or force for political ends – is immutable. For him “[f]our elements form the climate [or nature] of war: danger, exertion, uncertainty, and chance.”¹ However, the character of war, how war is fought, changes over time: the strategies planned, the policies derived, the tactics, techniques and procedures executed as well as the equipment, both hardware and these days software, and the way it is deployed and used. Look how the development of the rifle, artillery, chemical weapons, trench warfare, the tank, aircraft, blitzkrieg, nuclear weapons, insurgencies and, in recent years, improvised explosive devices (IEDs) and now drones have all changed how war is fought, demonstrating that the character of war continually evolves. 

So, if our nation is worth fighting for, and war has a just cause, with the right intention and called by a legitimate authority (UK Government), thereby upholding the basic tenets of CJWT, then it must also be conducted morally, with UK troops upholding the highest standards, even where international and national law is lacking or ambiguous. Those same combatants, however, deserve honourable decision-makers, the best moral foundations, the best education and training, and the best equipment and support possible. In military terms, that is the optimal fighting power, which is the ability of our Armed Forces to shape, contest and fight; it represents three interrelated components of the moral, conceptual and physical. 

The following essay considers how the changing character of war affects the moral component of fighting power and, in asking our troops to fight, how we should also prepare them for the realities of war, so that they do the right thing and are less likely to be traumatised by the aftereffects of conflict. It focuses on the discrimination between combatant and non-combatant, ensuring that only the former is intentionally targeted and that as much as possible is done first, to prevent collateral damage to non-combatants and civilian facilities, and second, to ensure that any attack is proportionate to the intended outcome. In so doing, it offers the potential to build resilience in combatants and lessen the potential aftereffects on the mind and issues with mental health.

The UK Armed Forces’ values and standards, which every service member is expected to adopt, are totally compatible with CJWT and the laws of war. The Army’s for example are: respect for others, integrity, courage, discipline, loyalty and selfless commitment. Soldiers that do not demonstrate such values and standards are generally unsuccessful in developing their careers, either removing themselves or being removed from service, if necessary, by lawful discharge following an offence or behaviour that brings the Army’s reputation into disrepute. However, and notwithstanding holding to a set of such values and standards, moral decision-making can be very difficult, as can distinguishing combatant from non-combatant in modern conflict, which has evolved a new lexicon of terminology to assist in describing the evolving character and types of war, or parts thereof, including new wars, unequal wars, small wars, hybrid war, fourth-generation warfare, war among the people, grey zones and so on. For discrimination and proportionality to be effective, combatant behaviour is key. 

Referring to the British Army’s values and standards, a former head of the British Army, General Sir Nicholas Carter, stated that the role of the Army “is to close with and kill the Queen’s enemies, and we have to have that at the forefront of our mind, but equally we cannot accept unacceptable behaviour.”² Similar comments were made last year on unacceptable behaviour by the current head of the British Army, General Sir Roly Walker.³ Indiscriminate targeting is clearly unacceptable behaviour in war, as is not minimising collateral damage. However, discrimination in modern conflict is much more demanding and obfuscate than in more conventional conflicts where one’s enemies are easily distinguishable. Current moral discourse and doctrines on discrimination are inadequate for combatants on the modern battlefield. 

Historic conventions and the laws of war have not kept pace with its changing character, which is to be expected. The prohibition of chemical weapons, for example, was not ratified for over 80 years after their first introduction during World War One. The UK’s latest publication covering the law of armed conflict, Joint Service Publication 383,⁴ goes back to 2004, and while amendments have been made, they are insufficient in clarifying rules for distinguishing combatant from non-combatant in complex modern conflict. With international law not keeping pace with the fast-changing character of war, moral revision, updating laws and conventions are essential, because the military doctrines of nations are based on and directed by adherence to them, which in turn guide ethical tactics, techniques and procedures for fighting troops.

All nations have a moral obligation and responsibility to prepare their forces for the potential horrors of conflict and provide them with the physical, conceptual and moral tools to perform their tasks – that is to optimise their fighting power according to the laws of war – including discriminate targeting and minimising collateral damage. They also have a responsibility for their mental wellbeing after conflict and protection from vexatious and unlawful claims. Consider the example of former soldier Dennis Hutchings, who faced prosecution over the 1974 shooting of John Pat Cunningham during the Northern Ireland Troubles. He had already been investigated several times and cleared, yet was pursued again more than four decades later, despite his age and poor health. Hutchings denied wrongdoing and said he had acted as a soldier on duty. He died in 2021, aged 80, after contracting Covid-19 while his trial was underway. Witnessing troops and veterans fearful of reprisals and unsupported by the Government is unlikely to encourage recruiting, even at a time of great need.

Lessons can be learned to improve fighting power in all three components (that is, the physical, conceptual and moral) to reduce physical and mental injury. During the latest wars in Iraq and Afghanistan, British forces recognised their shortcomings in the physical component of fighting power. Main battle tanks, for example, were of limited use during the insurgency that followed the initial conventional campaign in Iraq in 2003 – as they were similarly during the whole Afghanistan campaign. The UK’s modified patrol vehicle in Iraq, the SNATCH Landrover, colloquially known as the ‘mobile coffin’ by troops because of its limited protection against IEDs and other insurgent weapons, was totally inadequate for this new character of war. Quickly, new ranges of patrol and troop-carrying vehicles were developed, with greater ground clearance and v-shaped hulls to reduce and deflect the blast from IEDs. Bar, slat or stand-off armour, which resembles grills or metal meshes, were attached to vehicle exteriors at a stand-off distance, designed to initiate rocket propelled grenades prematurely. The design means that the shaped-charge warhead, focusing explosive energy into a thin penetrating ‘jet’, degrades sufficiently before reaching the intrinsic armour of the vehicle so that total penetration is not attainable. 

Likewise, a conceptual component for defeating the IED network holistically was developed for this character of war, based on tackling three lines of operation simultaneously: 

1. Defeat the device;
2. Train the force;
3. And attack the network. 

There remains, however, between the moral and conceptual components, a shortfall in morality, law, conventions and doctrines that adequately distinguish combatants from non-combatants; sufficient, that is, for it to be readily interpretable by soldiers. Greater clarity is necessary to: 

1. Prevent innocent deaths and maintain the support of local civilians; 
2. Prevent the effects of trauma and disorder caused by troops witnessing their own initiated collateral damage; 
3. And reduce the likelihood of soldiers being hounded and traumatised by inquiries years, if not decades, after their occurrence (such as Dennis Hutchings).

The UK Ministry of Defence (MOD) established the Iraq Historic Allegations Team (IHAT) to review and investigate allegations of abuse by UK Armed Forces personnel in Iraq, consistent with its obligations for compliance with the European Convention of Human Rights. Following a ten-month parliamentary inquiry, IHAT was condemned and the MOD blamed for facilitating spurious cases against British troops. The Inquiry chairman concluded that “there has been an almost total disregard of the welfare of soldiers and their families. The MoD must take responsibility for allowing this to happen.”⁵

Combatants can be severely traumatised by unwittingly killing civilians to a level associated with the context of their deaths. Professional and well-trained troops are aware that unintended incidents occur in conflicts, which they can endure as a feature of its immutable nature. Similarly, the foreseen but unintended killing of civilians as collateral damage is a situation that most combatants are able to tolerate as a reality of the horrors of war. However, no matter how unintended a civilian’s death, the soldier’s trauma, suffering and speed of recovery following such an event will depend largely on their reflecting clear observance to lawful orders, the inevitability of the civilian casualties as consequence of achieving a military objective (unintended, whether foreseeable or not), and the fog of war that surrounds such activities. What is clear is that the levels of post-traumatic stress disorder (PTSD) and suicides in serving military personnel and veterans have increased during and following conflicts in Iraq and Afghanistan and, while the reasons are complex and multiple, one component is their reflections on collateral damage. 

A consequence of failing to provide clarity to discrimination is to add to the increasing number of serving soldiers and veterans suffering PTSD, stress-related illnesses and suicide. In 2012, “BBC Panorama learned that 21 serving soldiers killed themselves… along with 29 veterans”,⁶ while 44 service personnel died in Afghanistan. Furthermore, investigations into violent offending by veterans of the Iraq and Afghanistan conflicts conclude that PTSD “is also a risk factor for violence.”⁷ Compared with regular forces, “Reservists have an increased prevalence of mental illness post-deployment.”⁸ However, some research shows remarkable resilience within UK military personnel despite considerable exposure to multiple traumatic events in recent conflicts, with the stark exception of alcohol misuse on return, which can lead to a mix of violence, sexual offending, family breakdown, homelessness and gaol. 

As awareness of stress-related illnesses has grown, nations have sought to identify and address causes and mitigate effects. Following on from the work of psychiatrist Jonathan Shay, who worked with Vietnam veterans and first coined the phrase ‘moral injury’, William Nash, a retired US Navy psychiatrist developed the concept further, to assist with understanding the self-harm phenomenon. For Nash and colleagues, moral injury arises from: “Potentially morally injurious events, such as perpetrating, failing to prevent, or bearing witness to acts that transgress deeply held moral beliefs and expectations may be deleterious in the long-term, emotionally, psychologically, behaviorally, spiritually, and socially.”⁹ In other words, the sense of moral certainty is broken. A deduction is that the greater the moral certainty, the less likelihood of combatants suffering psychological damage from exposure to the worst excesses of conflict, leading to self-harm and even suicide. 

Establishing a greater moral certainty during peacetime enables its continuance during conflict. CJWT is a mature moral framework and a developed form for today has the potential to assist in establishing greater moral certainty. Western culture’s CJWT, accompanied by values and standards that emanate from it, enable moral decisions when they need to be made quickly, sometimes instantly, and when the rules are less than clear. In turn, a developed form of CJWT can deliver greater moral certainty and clearer moral decision-making surrounding discrimination and collateral damage. Nash also notes that, rather than fear of death in battle, it is feelings of shame and guilt associated with moral injury that often cause psychiatric problems in conflict.¹⁰ Alongside the deaths of colleagues, which are recognised as a primary source of psychological trauma, psychiatrists identify guilt as another significant contributing factor, particularly when service personnel become aware that a military action has resulted in the collateral deaths of civilians, especially women and children. The right intention to minimise collateral damage also helps reduce the effects of moral injury. 

This example of strategic intent – with collateral damage directly related to moral injury and stress-related illnesses – refutes any premise that UK forces would benefit from a lenient or permissive attitude to collateral damage or retribution. It is militarily and practically counterproductive to harm civilians because soldiers lost through stress-related injuries, caused even partially by witnessing collateral damage, are no longer available to perform military tasks. After sentencing the first British soldier ever to be convicted of a war crime in 2007, the judge, Mr Justice McKinnon, said that not only was the reputation of British troops harmed but also that it “could put the lives of other British service personnel at risk and hamper future operations.”¹¹ With external bodies also aware that purposely harming civilians is militarily counterproductive – in seeking the hearts and minds of the population and, in this case, preventing future trauma for military witnesses to such events – the need for greater moral certainty grows. The negative impact on the livelihoods of veterans, who suffer stress-related illnesses from experiencing collateral damage, further counters any suggestion that British forces do not sincerely seek to discriminate and minimise collateral damage.

Soldiers, therefore, need revised physical, conceptual and moral components, skills and tools to achieve their military objectives discriminately in modern conflict; education, training and direction that is more clearly defined and easily interpretable, enabling the minimising of collateral damage, preventing their own moral injuries and the consequences of stress-related illnesses. Writing in 2008, Michael Mazarr summarised the inadequacy of applying US military forces to asymmetric conflict as follows: 

As smart, adaptable, and courageous as U.S. military officers and men and women clearly are and will be, asymmetric challenges demand asymmetric responses—political, economic, cultural, informational, and psychological tools, tactics, and techniques allowed to work organically over time, not retrained military forces whose true purpose is to fight and win wars, which are different enterprises. The strategic trap is obvious: Furnished with a vast, expensive, skillful military tool, policymakers will use it again and again, as they have been doing, without confronting the tougher challenge of shifting resources into nonmilitary tools of statecraft.¹²

Mazarr is surely right in appreciating that the challenges of asymmetric war require targeted responses, which try to capture and address all the components that create and fuel it. He is right to concede that conventional military personnel are not ideally prepared to achieve some of the “political, economic, cultural, informational, and psychological tools, tactics, and techniques” necessary to overcome the challenges of modern conflict – they prepare and train for conventional war. He is, however, naïve to withhold military force from his list of asymmetric responses – the challenges that he identifies exclude a significant fighting component, otherwise it is not war. The latest conflicts in Iraq, Afghanistan and against ISIL¹³ demonstrate this abundantly, and no matter the fighting power of weaker sides in an asymmetric war, using military or improvised ordnance, enforcing security is essential and a particular skill of militaries. While weaker sides continue to pose a war-fighting capacity, stronger forces will need to defeat them, requiring discriminate targeting and establishing a secure setting in order to enable “nonmilitary tools of statecraft.”

Following the fall of the Berlin Wall in 1989, Britain and its allies have evolved smaller armies, with multiple roles, in complex hostile environments and with evermore scrutiny. It is likely that soldiers will continue to deploy across the full spectrum of conflict, from high-intensity conventional war to peacekeeping and every hybrid and asymmetric variant in between, and simultaneously. If the modern combatant must perform duties commensurate with these challenges and implement right actions, with limited preparation and laws that are currently centred on conventional conflict, then a morally sound base on which to deliver virtue ethics is an optimal toolkit. They deserve moral preparation, belief in the integrity of the law, clear orders that are easily intelligible for the level of their competencies, and trust that they will not be hounded in future years for their moral and lawful actions at the time. 

In conclusion, if we accept that Britain is worth fighting for and needs a military to deter its enemies and, if necessary, defend its people, then its combatants need clarity of orders, responsibilities and boundaries to achieve military objectives, which reduce ambiguity in thought and action, and in turn enable efficiency, effectiveness and minimal casualties; reducing the likelihood of stress-related disorders, resulting from their experience of collateral damage is a corollary. Put another way, trauma and disorder, caused in part by witnessing collateral damage, are less likely if rules of engagement are clearer and more interpretable, and combatants are morally robust and attuned to their values and standards. A sound moral framework, such as CJWT, underpins development in the laws of war and conventions and, in turn, formulation of military doctrines, reflective of those morals in the contemporary age. Discrimination in modern war needs to be developed and interpreted so that it enables and even compels combatant compliance, is easy to interpret as stated, but also can be more clearly recognisable and verifiable as right intention by a third party – maybe artificial intelligence has a role to play here. 

Combatants dispatched to apply military force must believe and have the confidence to know that, should their discriminatory actions lead to foreseen but unintended collateral damage, those same actions were morally and legally supportable, and are not open to future bogus claims and scrutiny. When there are shortcomings in the laws of war, as there always are, and our sailors, soldiers, aviators and marines are at war, then there must be a moral framework to guide them. Troops cannot be made accountable now or anytime in the future, when acting morally, if laws are unavailable or ambiguous in the contemporary context that they find themselves. For Aquinas: “And yet even those who make sinful use of the sword are not always slain with the sword, yet they always perish with their own sword, because, unless they repent, they are punished eternally for their sinful use of the sword.”¹⁴ Hence combatants need to ‘use the sword’ without sinning – and by God’s grace, they will be saved. 

Finally, the CJWT assumes that even a just war remains a tragic consequence of living in a fallen world. While militaries battle, non-combatant Christians, whether they support war or not, are called to engage spiritually with it through prayer. In Exodus 17:8-13, Joshua fights the Amalekites while Moses intercedes before God. The victory is linked both to the military action and to prayer. 

After British forces were forced to retreat to Dunkirk in 1940, King George VI called for a National Day of Prayer on 26 May 1940. Millions responded and two events immediately followed. First, a violent storm arose over the Dunkirk region grounding the Luftwaffe, which had been causing thousands of British casualties on the beaches. Second, a great calm descended on the Channel. Together, these prayer-answered interventions allowed hundreds of tiny boats to sail across the Channel and rescue around 335,000 soldiers. This was the ‘the miracle of Dunkirk’. Prayer for our Armed Forces personnel is just as necessary today, for the sailors onboard HMS Dragon, the soldiers in Estonia and aviators in Qatar, as well as every other combatant on operations or preparing for operations in the UK and abroad. We know that God answers prayer, our troops are worthy of prayer, and Christians in our nation are encouraged to pray for those that selflessly commit to protecting Britain and its overseas territories, even unto death. Let us unite in prayer for our Armed Forces, that those who defend our nation may know God’s protection, wisdom and peace, and also for every opportunity to bring Christ’s hope, comfort and gospel truth to those who serve our nation.

You can learn more about SASRA’s growing work with our Armed Forces at sasra.org.uk.

1. Carl von Clausewitz, On War, trans. Michael Howard and Peter Paret (Princeton University Press, 2008), ‘On Military Genius’, https://ereader.perlego.com/1/book/735246. ↩︎
2. ‘Army Head Launches “crackdown” on Bullying and Harassment’, UK, BBC News, 4 September 2015, https://www.bbc.co.uk/news/uk-34148307. ↩︎
3. See for instance: ‘Baked-in Behaviour: Army Boss Lays Bare the Challenge of Training Recruits Who Already Hold Negative Views of Women’, Soldier Magazine, April 2025, https://soldier.army.mod.uk/issues/april-2025/updates/baked-in-behaviour. ↩︎
4. ‘Manual of the Law of Armed Conflict (JSP 383)’, GOV.UK, Ministry of Defence (UK), 28 August 2013, https://www.gov.uk/government/collections/jsp-383. ↩︎
5. Robert Mendick, ‘Iraq Abuse Inquiry to Shut after MPs Find It Has “Directly Harmed Defence of Our Nation”‘, The Telegraph, 10 February 2017, https://www.telegraph.co.uk/news/2017/02/10/iraq-abuse-inquiry-has-directly-harmed-defence-nation-andmust/. ↩︎
6. ‘UK Soldier and Veteran Suicides “Outstrip Afghan Deaths”‘, UK, BBC News, 13 July 2013, https://www.bbc.co.uk/news/uk-23259865. ↩︎
7. Deidre MacManus et al., ‘Violent Offending by UK Military Personnel Deployed to Iraq and Afghanistan: A Data Linkage Cohort Study’, The Lancet 381, no. 9870 (2013): 907, http://thelancet.com/pdfs/journals/lancet/PIIS0140-6736(13)60354-2.pdf. ↩︎
8. Deirdre MacManus et al., ‘The Mental Health of the UK Armed Forces in the 21st Century: Resilience in the Face of Adversity’, Review, BMJ Military Health 160, no. 2 (2014): 125–30, https://doi.org/10.1136/jramc-2013-000213. ↩︎
9. Brett T. Litz et al.,’Moral Injury and Moral Repair in War Veterans: A Preliminary Model and Intervention Strategy’, Clinical Psychology Review, Posttraumatic Stress Disorder and the Wars in Afghanistan and Iraq, vol. 29, no. 8 (2009): 695–706, https://doi.org/10.1016/j.cpr.2009.07.003. ↩︎
10. Litz et al., ‘Moral Injury and Moral Repair in War Veterans’. ↩︎
11. Steven Morris, ‘First British Soldier to Be Convicted of a War Crime Is Jailed for Ill-Treatment of Iraqi Civilians’, UK News, The Guardian, 30 April 2007, https://www.theguardian.com/uk/2007/may/01/military.iraq. ↩︎
12. Michael J. Mazarr, ‘The Folly of “Asymmetric War”‘, The Washington Quarterly 31, no. 3 (2008): 38, https://csis-website-prod.s3.amazonaws.com/s3fs-public/legacy_files/files/publication/twq08summermazarr.pdf. ↩︎
13. The Islamic State of Iraq and the Levant. ↩︎
14. St Thomas Aquinas, Summa Theologica Part II (Jazzybee Verlag, 2012), ‘First Article [II-II. Q. 40. Art. 1]’, https://ereader.perlego.com/1/book/1071840. ↩︎