The City, Battlefield of the 21st Century: Why the Law Struggles to Protect Civilians
From Mosul to Aleppo, from Gaza to the cities of Ukraine, war has moved into the heart of the city. Yet it is precisely there that the principles of international humanitarian law — distinction, proportionality, precaution — are hardest to uphold.
By 2030, two-thirds of humanity will live in cities. As a mechanical consequence, wars are increasingly fought there — no longer to capture the city, but within its streets, its buildings, its basements. Yet the city is the environment in which the law of war is hardest to apply. To understand why is to grasp one of the great humanitarian challenges of our century.
For a long time, military doctrine regarded the city as a space to be avoided. Sun Tzu already advised against sieges; the city was a refuge within walls, rarely a place of battle. That era is over. From Stalingrad to Mosul, from Aleppo to Gaza, the urban fabric has become the theatre of direct combat. And as the world’s major crisis zones grow more urbanized, this trend will only intensify.
Why the city changes everything
One principle sums up the difficulty: the city is, by nature, civilian. It is built to be inhabited, not to be defended. Combatants, civilians and civilian objects intermingle there, sometimes indistinguishably. And in this disorder, it is almost always civilians who pay the heaviest price.
The city also reshapes the balance of power. A technically inferior adversary can there challenge an advanced army: it knows the terrain, conceals itself within it, moves through it out of sight. The urban environment reduces the effectiveness of surveillance, intelligence, air support and stand-off strikes — it nullifies, at least in part, the attacker’s material superiority. As the architect Eyal Weizman, a specialist in urban conflict, puts it: whoever controls the means of circulation controls the city.
It is in this context that the three pillars of international humanitarian law (IHL) — distinction, proportionality, precaution — must apply. And it is here that they falter.
Distinction: who is a civilian, what is military?
The principle of distinction requires that only military objectives be targeted, never civilians or their property. In the city, it runs up against two practical impossibilities.
Distinguishing targets. Military infrastructure (headquarters, barracks) is woven into the urban grid, often installed in buildings originally intended for civilian use. Above all, much infrastructure is dual-use: a power plant may supply both a military base and a hospital. To strike it may achieve a military objective — but it may also cut off electricity to an entire neighbourhood, with cascading consequences for public health.
Distinguishing persons. In a non-international armed conflict, the very notion of “combatant” does not exist: an individual may be targeted only on account of his direct participation in hostilities. And that participation is governed by three cumulative criteria — a threshold of harm, a direct causal link, and a belligerent nexus. Supplying water or political support to an armed group is not enough; there must be an act causing real harm. In the city, distinguishing direct assistance from indirect assistance, a combatant bearing no distinctive sign from an ordinary resident, is often impossible.
To this is added the question of human shields. IHL prohibits their use in international conflicts (art. 28 GC IV, art. 51(7) AP I). But a dangerous rhetoric has taken hold: speaking of “eliminating human shields” rather than “killing civilians” makes it possible to shift responsibility for losses onto the enemy — a semantic construction that, in practice, loosens the requirements of distinction and proportionality.
Proportionality and precaution: a calculation become impossible
The principle of proportionality prohibits an attack that would cause excessive civilian losses in relation to the concrete and direct military advantage anticipated. It is a judgement of balance — profoundly human, contextual, difficult to program or automate.
In the city, this calculation is complicated by a factor too often overlooked: cascading effects. Urban systems (water, energy, health, sanitation) are interdependent. To destroy one node is to set off a chain reaction whose victims continue to be counted long after the strike — through disease, displacement, the collapse of daily life. Proportionality requires anticipating these repercussions, insofar as they are reasonably foreseeable. Few operations do so in earnest.
The principle of precaution, finally, requires constant measures to spare civilians — in the attack as in its preparation. It presupposes locating objectives precisely, choosing the means and the timing, and desisting if the civilian cost is disproportionate. These are all requirements that urban confusion puts severely to the test.
A gap in the framework
One observation is unavoidable: there is no rule of IHL specifically dedicated to urban conflict — and there need not necessarily be one. The existing principles suffice, provided they are scrupulously observed. The problem, then, is not a legal vacuum but a deficit in application.
It is also worth recalling what IHL is: not a humanitarian absolute, but a balance between two logics. On one side, the principle of humanity, which seeks to reduce suffering; on the other, military necessity, which permits defeating the enemy at the least cost. The whole law of war rests in the tension between these two poles — and it is in the city, where everything intermingles, that this tension is at its sharpest.
This requirement is not only moral, it is strategic. The way an army conducts its urban operations engages its credibility, under the gaze of the media, of public opinion and of the courts. The protection of civilians is not an optional grace note: it conditions the legitimacy — and therefore the effectiveness — of military action. At a time when the city is establishing itself as the battlefield par excellence, to make it a blind spot of the law would be as much a failing as an abdication.
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