The first concept of necessity comes from just war theory, an ethical framework developed over centuries to evaluate whether the use of force can be morally justified (jus ad bellum).

One of its core tenets is necessity:

War must be a last resort, undertaken only after all nonviolent alternatives—diplomacy, deterrence, sanctions, international mediation—have been exhausted.

In the case of Israel, the record speaks for itself. Israel withdrew from Gaza in 2005, dismantling all civilian and military infrastructure. In the years that followed, Hamas seized power in a violent coup, launched tens of thousands of rockets and rejected every meaningful effort at peaceful coexistence. Despite periodic ceasefires and repeated international mediation, Hamas remained committed not to a Palestinian state alongside Israel—but to Israel’s destruction.

On Oct. 7, Hamas made its intentions unmistakable. It crossed the border not to challenge Israeli soldiers, but to massacre civilians. It filmed the atrocities and vowed to do it again. In that context, the claim that Israel’s military response lacked moral necessity ignores the facts and defies common sense.

2. Legal necessity — the law of armed conflict

The second form of necessity is not philosophical but legal. It belongs to the realm of international humanitarian law (IHL)—the rules governing the conduct of war (jus in bello).

Military necessity permits only those actions required to achieve a legitimate military objective.

This principle—codified in the Geneva Conventions, Hague Regulations and customary international law—does not allow destruction for its own sake. It does not excuse harm to civilians unless it is incidental to a lawful strike. And it certainly does not override the obligations to distinguish between military and civilian targets or to avoid disproportionate attacks.

Every Israeli military operation in Gaza is bound by this standard. It is not enough to identify a Hamas presence in a building or a neighborhood. To strike lawfully, the target must provide a concrete and direct military advantage, and every feasible precaution must be taken to mitigate civilian harm.

Israel’s military attorneys and commanders operate within this framework. Target selection, weapon choice, timing of attack, and warning mechanisms are scrutinized in real time. The Israel Defense Forces not only operates under legal necessity—it documents and reviews its actions at a level few modern militaries do, particularly when fighting a terrorist group embedded in a civilian population.

The bridge vs. the bakery

A useful example from the laws of war helps clarify this distinction.

Destroying a bridge used to transport enemy weapons is a lawful act of military necessity. It offers a clear operational advantage and directly degrades enemy capability. By contrast, destroying a bakery in a residential neighborhood simply because enemy fighters may stop there for food is not. The bakery is not a military objective, and its destruction would serve no legitimate military purpose.

This distinction matters in urban warfare. In Gaza, where Hamas routinely embeds its military assets within civilian areas—using schools, homes and mosques—Israel faces extraordinary challenges. But the legal standards do not change. Every action must meet the test of military necessity. Every strike must be tied to a legitimate objective. The presence of civilians demands restraint, even when facing an adversary that deliberately exploits them.

Necessary war, constrained conduct

So, was Israel’s war against Hamas necessary?

That depends on which kind of necessity you mean. But in truth, it meets both tests:

Was the war morally necessary? After Oct. 7—following the deliberate massacre of civilians, the kidnapping of hostages, and Hamas’s declared intention to repeat those atrocities—the answer is unequivocally yes.

Are Israel’s military operations legally necessary? While each strike must meet specific legal thresholds, the IDF operates under one of the most stringent legal and ethical frameworks in modern warfare. It is bound by the law of armed conflict and has demonstrated an unprecedented commitment to minimizing harm, even while engaging an enemy that hides among civilians and violates every rule of war.

A war can be both morally justified and legally constrained. Israel’s campaign against Hamas is exactly that. It was not launched lightly or recklessly—it was waged in defense of life, sovereignty and the rule of law.

Anyone asking whether Israel’s war was necessary should first understand what they are really asking—and then recognize that the answer, by every standard that matters, is yes.

The article was written by Arsen Ostrovsky together with retired United States Army major and urban warfare expert John Spencer John Spencer.

Published in JNS, April  20, 2025.