Do we still expect states to fight just wars? If so, does this explain why reports of military atrocities still have the power to shock? That shock and disappointment derives, in part, from a widespread and fundamental misunderstanding about the nature and purpose of ‘just wars’.

So-called ius ad bellum conditions – that is, the rights or justice required to go to war in the first place – are susceptible to subjective national interest. Indeed, it is a truism of military conflict that every state believes itself to be fighting a ‘just war’. Meanwhile, ius in bello principles – the moral and legal norms governing proper military conduct – seem even more fragile. Expectations regarding the immunity of non-combatant persons and property, protections for prisoners of war, and the proportionality of violence all frequently disappoint in practice. The Russian invasion of Ukraine, the recent slaughter of Israeli civilians by Hamas, and the ongoing Israeli ‘Iron Swords’ operation in Gaza are just the latest reminders that legal and ethical safeguards restricting the declaration and conduct of war are far from guaranteed.

The purpose of the military is ‘to kill people and break things’. While many commanders would cringe at this flippant maxim, the fact remains that the essential purpose of war is the application of massive force to achieve certain objectives. This cannot be done without killing people or breaking things, frequently on a vast scale. Even the most idealistic polities can’t escape this basic fact.

The remarkable thing about war, therefore, is not that it is destructive and brutal – for such is the nature of the beast – but that any regulations or restrictions exist in the first place.

As an ethical position, absolute pacifism rejects the justification of war in all its forms, yet there have been and are exceedingly few people (let alone states) willing to pursue genuinely pacifist responses to violence. Nonetheless, religious, ethical, and legal engagement with the potential justifications of warfare have been, and continue to be, common throughout history. Around the world, political and religious communities have distinguished between morally ‘good’ and ‘bad’ wars, demonstrating a clear preference for conceptualising war as an ethical and legal enterprise.

How far back in time do we need to look for the origins of such thought about ‘just’ and ‘unjust’ wars? The answer is a long way back indeed: over 5,000 years, to the close of the fourth millennium BC. Moreover, what is apparent when examining the origins of just war doctrine is that just wars were never conceptualised as, or intended to be, ‘limited’ wars.

Just war doctrines emerged in the ancient world from around 3000 BC. Egypt provides the earliest evidence of ethical thought about war, but similar ideas soon developed throughout Mesopotamia, Anatolia, and the Levant. Of particular note are the large number of texts and material evidence hailing from the great kingdoms of Hatti (c. 1650-1200 BC) and Neo-Assyria (c. 900-600 BC), as well as the mythical-religious texts of the ancient Israelites, collected together in the mid-first millennium BC to form the Tanakh (Hebrew Bible). Just war thought also emerged in China from the sixth century BC in Confucian, Mohist, Daoist, and Legalist works; and from around the same time in India, in the Sanskrit epics of the Rāmāyana and Mahābhārata.

From at least 3100 BC, Egyptian royal ideology promoted the divinely mandated authority of the pharaoh to wage war. The physical defence of Egypt was even conceived on a cosmological level, with the territorial defence of Egypt also constituting the defence of Ma’at (order, justice, righteousness) against the destructive power of Isfet (chaos, injustice, evil). Egyptian sources talk a great deal about just causes, such as self-defence and defence of allies, as well as both punitive and vindictive justice. Because Egypt saw itself as sitting atop the cosmological pyramid – representing the pinnacle of civilised morality – Egyptian wars were viewed as intrinsically just. Egypt’s contempt for the ‘evil foreigner’ endowed the state with an uncontested legitimacy to assert itself – reactively or proactively – against external ‘barbarism’. In effect, every Egyptian war was understood as defensive (even if it was patently offensive) and every Egyptian war was ‘just’.

From c.1650 BC, the Hittites – an Anatolian civilisation occupying much of what is now Turkey and Syria – developed a complex and sophisticated range of considerations concerning whether or not a war was just. The authority of the king as a representative of the gods was crucial, and the Hittites were sensitive to the notion that just wars had to have just causes. Self-defence was the principal cause for war, but the restitution of property, vengeance for divine and mundane injuries (especially oath violation), and the defence of allies all ranked as important reasons to wage war. For the Hittites, war was regarded as a legal process, prosecuted in the court of the gods. To win in war, one had to be righteous, both in the personal moral qualities of the king as well as the legitimacy of the cause for which he was fighting.

Crucially, the Hittites made a conceptual leap in just-war thought by recognising that they themselves could commit errors and engage in unjust wars. This witnessed the first serious engagement with international justice as something more objective rather than wholly chauvinistic and geared towards the interest of the home nation. The importance of this development cannot be overstated.

In contrast, ancient Israelite concepts of just war mirrored the Egyptian approach, remaining highly partisan and absolutist. While Yahweh was the ultimate authority and arbiter of justice, his anointed ruler – whether a ‘judge’ such as Joshua or a monarch like David – could wage war under his authority and according to his commands. Defence of territory and retributive vengeance were at the forefront of Israelite conceptions of just warfare; indeed, vengeance for perceived injuries against Yahweh (rather than the Israelites themselves) were seen as justifying wars of extermination against Israel’s enemies in Canaan. Yet, as in Hatti, the Israelites recognised their own capacity for sin. Commoners and kings were capable of sin and, as the story of Israel, Samaria and Judah unfolds in the Tanakh, these sins became increasingly stark, leading ultimately to the destruction of the Israelite kingdoms and the humiliation of their peoples. Nevertheless, while Israel’s enemies might triumph, it was emphatically not because they were righteous or held a legitimate political grievance. Just like the ancient Egyptian perception of foreigners as representative of Isfet, Israelite thought perceived all non-Yahweh, non-Israelite peoples as inferior, destructive, and unjust. Israel’s enemies were not considered righteous or justified, but could be used by Yahweh as a punitive rod to beat his wayward people.

Ancient Egyptians, Hittites, and Israelites developed sophisticated ius ad bellum traditions built on complex moral, legal, religious, and ideological foundations. Unfortunately, such was the strength of these ad bellum traditions that ius in bello doctrines were almost completely ignored. With just wars conceived on a cosmic level, there was little chance of affording the enemy any protections. Ancient just wars were understood as absolutist struggles between good and evil, which required the annihilation of the enemy.

Throughout the ancient Near East there were no prohibitions on weapons or tactics. Summary execution on or off the battlefield was possible, although mass enslavement was more likely. Enemy corpses were routinely mutilated, as hands, ears, feet or phalli could be collected to monitor the number of enemy dead and reward soldiers accordingly. There was no distinction between combatants and non-combatants. Women and children enjoyed no immunities and were frequently targeted as desirable slaves. All enemy property – movable and immovable – was considered a legitimate target, and plunder was an important component of war for commanders and soldiers alike.

Only the flimsiest traces of in bello norms existed. These included a general but not universal agreement that war should be properly declared. Diplomatic envoys were also routinely granted safe conducts during peacetime, but during wartime these could be ignored. In sum, there was no substantive ancient ius in bello tradition.

Yet military restraint was commonly practised. This was not motivated by ethical, ideological, or religious convictions, but was rooted in military and political pragmatism. For example, the vaunted prescriptions of Deuteronomy 20 and 21, on closer inspection, are not substantive ethical norms but rather pragmatic military instructions for siege warfare (Deut 20) and taboo-based concerns for the integration of non-Israelite female sex-slaves into Israelite communities (Deut 21). The fact was, not every enemy could be annihilated, nor every individual enslaved, and not every enemy ruler toppled. It could be far more practical and profitable to stay one’s hand. This leaves us with the counter-intuitive conclusion that the conduct of ancient Near Eastern warfare was actually less brutal than ancient Near Eastern just war doctrine permitted.

Why is any of this relevant to modern international relations and armed conflict? First, because there’s evidence that much later thought on just war – including the Greco-Roman, Judeo-Christian, and Islamic traditions – has its roots in these archaic Near Eastern doctrines, creating an intellectual lineage that stretches all the way up to modern just war theory and international laws of armed conflict.

Second, because many of the most dangerous characteristics of ancient just war thought are worryingly apparent in modern just war theory and international politics. We’ve seen that ancient justifications of war were so absolutist and partisan, so convinced of their own moral authority, that they suffocated the emergence of in bello norms. Likewise, in modern conflicts humanitarian restraints are more likely to be ignored when states are convinced of their own moral superiority and justification. When the desire to wreak vengeance upon the ‘barbarian’ becomes overwhelming (drowning out more cautious voices and blotting out contextualisation) there is little left to constrain the violence of war. We witnessed this in the United States’ response to 9/11; we may be witnessing it in Gaza.

As far as contemporary just war theory is concerned, there has also been a significant turn over the last two decades. The so-called War Convention protects the legal equality of combatants regardless of whether they’re deemed to be fighting a just or unjust war.

An influential ‘revisionist’ camp of scholars has, however, emphasised the culpabilities and liabilities of individuals in war. Approaching the problem from the perspective of analytical moral philosophy, commentators such as Jeff McMahan, Helen Frowe, David Rodin, and Seth Lazar (among others) have mounted a challenge to the War Convention, arguing that the moral and legal status of combatants in war is not symmetrical, but rather asymmetrical: unjust combatants are culpable and thus liable to harm; just combatants are innocent and therefore not liable to harm. Controversially, revisionists have argued that this distinction extends to certain ‘unjust’ civilians and prisoners of war, so that, under certain circumstances, killing such individuals could be considered perfectly licit.

Insisting that war is an arena in which universal or absolute moral truths can be applied is worryingly reminiscent of the types of just war thought which first emerged in the ancient Near East. The potential for the deliberate or careless slaughter of people branded as unjust and wicked is rooted in historical precedent. We need to be acutely aware and exceedingly sceptical of the rhetoric of just war when coming from the mouths of politicians and military commanders. All too often, it seems, it is a pretext for a form of unlimited violence that betrays the moral and legal foundations upon which our societies are built.