In times of peace and prosperity, it is easy for scholars to forget that at their deepest level, states exist to provide order and protection for their inhabitants and focus attention instead on the claims of justice and equality. It is probably true that in direct proportion to the distance a writer sits from harm’s way, the simpler crafting and then applying a conception of just war seems.

The various strands of the just war tradition in themselves present a curious mix of justification for state action and ethical guidance to practitioners. The justificatory side of the tradition is almost as useless as a practical matter. No one in power elects to start a war they see as truly unjust, and at best, one can try to persuade the population forced to fight that their cause deserves no moral sanction. Tyrants may deny that rules of justice apply—that the strong do what they will and the weak suffer what they must—but even Vladimir Putin has argued for the righteousness of his cause. Most of the time, the leadership on both sides in a war are fully convinced of the justice of their cause.

Just war doctrines find a readier audience when it comes to the actual practice in combat, and most students and military professionals accept the argument that the means a nation or movement deploys in combat can color or delegitimize the ends they seek.

As Israel responds to Hamas’s brutality, we will increasingly see commentators and politicians argue that war is not the answer, that a cease-fire is in everyone’s best interests, and especially, that Israel’s combat operations are disproportionate to the situation or violate the norms of war. No reasonable person denies that states should be forced to endure atrocities without response. It shouldn’t have to be said (but seemingly does) that Israel’s declaration of war on Hamas is entirely justified. We should be clear about what this authorizes them to do, however, and clearly understand what a “proportional” response entails. In his classic Just and Unjust Wars, Michael Walzer writes:

We must grant that soldiers are entitled to try to win the wars they are entitled to fight. That means that they can do what they must to win; they can do their utmost, so long as what they do is actually related to winning. Indeed, they should do their utmost, so as to end the fighting as quickly as possible. The rules of war rule out only purposeless or wanton violence.

Proportionality in the just war sense Walzer sets out here means that we ought to judge whatever operations Israel undertakes in terms of whether they will eliminate the threat Hamas poses—and of course, taken by itself, it suggests that Israel has a free hand within these limits. It is certainly true that the Israelis should avoid acts of cruelty or simple vengeance and spare the innocent wherever possible, but as they respond, we should also remember the degree to which Hamas has rendered it impossible for anyone to pursue them without killing large numbers of civilians. They must also seek to reestablish peace for Israel and seek an end to the war that makes that peace possible.

Western militaries operating within a just war framework tend to understand war as a coordinated but limited use of violence meant to achieve specific political ends. The moral frameworks that constitute the just war tradition implicitly assume certain basic limits, even if sometimes they are purely pragmatic ones driven by soldiers themselves. One does not kill or abuse the enemy’s wounded today because, in the chaos of war, you may find yourself at your enemy’s mercy tomorrow. Other precepts focus on respecting the humanity itself, as Walzer notes:

Lawyers sometimes talk as if the legal rules were simply humanitarian in character, as if the ban on rape or on the deliberate killing of civilians were nothing more than a piece of kindness. But when soldiers respect these bans, they are not acting kindly or gently or magnanimously; they are acting justly. If they are humanitarian soldiers, they may indeed do more than is required of them—sharing their food with civilians, for example, rather than merely not raping or killing them. But the ban on rape and murder is a matter of right.

However firmly philosophers state these rules, as a workable ethic, justice in war relies on reciprocity. When one side in a war begins with a gross violation, it is hard to see how that does not factor into the defender’s sense of what a proportional response entails.

In The Ethics of Insurgency, Michael L. Gross argued that unconventional warriors ought to be judged by similar constraints as those serving a nation-state:

Despite legitimate grievances, guerrillas do not always have cause to wage war. When they do, the method they choose should be the best: the one that promises to rectify legitimate grievances at the least cost. … Just guerrilla warfare strives for national self-determination and, like state warfare, will pursue those means, violent or nonviolent, that are cost-effective and respectful of the fundamental rights of combatants and noncombatants.

Hamas largely avoided military targets in their initial attacks. Instead, they focused on murdering, raping, and torturing innocents of all ages while also taking hostages back to Gaza. These are not incidental to other actions but the very core of their mission in ravaging Israeli settlements—and they shared large portions of it on social media with glee.

Indeed, Hamas’s strategy is one based around the comprehensive disrespect of the just war tradition. Their refrain of “from the river to the sea” is a clue to the absoluteness of their ambitions. In his Ethics of War, A. J. Coates argues that theological or ideological claims like this give rise to a militarism that renders war total, and one’s enemies absolute:

An absolute enemy is an enemy without rights against whom total war must be waged. Extermination is the only fate worthy of the “infidel,” the “AntiChrist,” “the Great Satan,” the “verminous Jew,” the “bourgeois,” the “Bolshevik,” the “Hun,” the “kulak,” the “untermensch.” In all its forms, dehumanization or demonization of the enemy leads to the barbarization of war.

Over the course of the last week, dozens of commentators have justified Hamas’s actions in terms of their greater cause of “liberation” or “decolonization.” Yale’s Zareena Grewal responded to those outraged at the attacks on innocents, “Settlers are not civilians. This is not hard.” This is precisely the sort of rhetoric that (quietly) insists that in pursuit of Hamas’s goals, any means are justifiable. We should also recognize that it is an aim that makes lasting peace in the region utterly impossible.

In these pages, David Goldman recently summarized Israel’s perilous situation:

For the time being, Israel will keep Gaza under siege. It has a grace period due to the world’s revulsion at Hamas, but this will not last forever. As pictures of starving Gazans circulate in the coming weeks, world sentiment once again will turn against the Israelis. If Israel cannot strike a killer blow against Hamas on the ground during the next few weeks, its strategic position will be permanently weakened.

The terrible events of the past several days make clear that the existential urges of the ancient world cannot be erased with the bland brush of modernity—something that the Serbs of Kosovo, the Armenians of Nagorno-Karabakh, and the Ukrainians of Donetsk, Luhansk, and Kherson learned already.

Israel aims at destroying a barbaric enemy who has entrenched themselves with hostages, and among their own civilian population—a people Hamas seems intent on keeping in harm’s way.

Just war has no meaning apart from the peace that nations seek through war. It remains to be seen what peace Israel can secure from this conflict. But minimally, a peace that fails to reestablish their security and deter future aggression will, as Goldman suggests, place them on a path to self-destruction. Hard choices lie ahead for Israel’s leaders. We should all pray that Israelis find ways to conduct their war with restraint, for they will bear the scars of this tragedy for generations to come, as well as the consequences of whatever peace they achieve, or don’t.