Israel is committing genocide against Palestinians in Gaza.

No genocide in the 20th century ended without armed intervention.

For more than a year now, the international community has been in denial about the implication of these two facts.

The international community has demanded that Israel stop. The international community has sued Israel. The International Criminal Court has issued warrants for the arrest of Israeli leaders. The UN Security Council has even voted unanimously for a ceasefire (with the United States vetoing, of course).

But even the most outspoken international lawyers dare not speak the name of the only thing that history suggests might actually stop Israel.

That is, of course, war—by the international community against Israel.

As months of genocide have turned into years, and the body count has soared from tens of thousands of Palestinians to hundreds of thousands with no end in sight, the international community is increasingly faced with a stark choice:

Either organize armed intervention to stop the genocide or give up on the view that genocide is against the law.

To be sure, this is not the first American-backed genocide of the Postwar era or the first time that America and Israel have ignored the demands of international institutions. But never before has the United States—the architect of the present international system—enthusiastically backed a genocide against the objection of every major organ of world government: the UN General Assembly, the UN Security Council, the International Court of Justice, and the International Criminal Court.

International lawyers like to pretend that international law is self-enforcing. They talk about “soft power”, custom, and the innate human tendency to follow rules even in the absence of an enforcement mechanism.

But human beings have another innate tendency: to measure the strength of a rule by the extent to which people are willing to fight to defend it. A rule honored only in spectacular breach stops being a rule.

The rule against genocide will not survive the extermination of two million people documented by the perpetrators themselves on social media while the world lifts a finger only to wag it back and forth.

Nor will American or Israeli policymakers save the international community from this choice.

History teaches that once a state goes all-in on genocide—as Israel and her American backer have over the past year—the only way it ends other than through war is completion.

It took the Allies’ invasion of Germany to end the Holocaust, Vietnam’s invasion of Cambodia to end the killing fields, the conquest of Rwanda by the Rwandan Patriotic Front to end the Rwandan Genocide, and the invasion of Palestine by Arab armies to halt Israel’s first attempt at genocide of Palestinians in 1948 during the Nakba.

By contrast, no one came to rescue the Armenians or the Bosnians. Those genocides ended only with the almost complete eradication of Armenian life in Turkey and Bosnian life in Srebrenica (until military intervention finally drove the Serbs from the region).

The lesson is clear: to stop the Palestinian Genocide, the world must go to war against Israel.

States could coordinate their efforts under the General Assembly’s “uniting for peace” resolution, which authorizes international military action to quell threats to international peace when the UN Security Council fails to act.

A UN force fought a bloody war on the Korean Peninsula in the early 1950s under the authority of that resolution. And in 1956 and 1957, another UN force organized under that resolution oversaw Israel’s withdrawal from Suez and Gaza after the Suez Crisis.

Even absent a resolution of the General Assembly, the mere declaration of war by a diverse international coalition might be enough to halt the slaughter. To date, fourteen countries have joined South Africa in charging Israel with genocide before the International Court of Justice.

These include three members of the European Union (Belgium, Spain, and Ireland), four Middle Eastern countries (including Turkey and Egypt), and six Latin American countries (including Mexico, Chile, and Colombia).

If these countries were to join South Africa in declaring war, Israel would face an international coalition with a combined GDP nearly ten times her own. If the coalition were to devote just 3% of its GDP to the war, that expenditure would dwarf Israeli military spending inclusive of American transfers over the past year.

More importantly, Israel’s American backer would face an unprecedented challenge to her authority on three continents.

At a time when America has been struggling to arm Israel, face down Russia in Ukraine, and deter China, it is difficult to imagine America isolating her Latin American neighbors, her European allies, and her Middle Eastern friends all at the same time—much less going to war against them.

American support for Israel is strong, but America has never been asked to pay a meaningful price for it. America’s unwillingness to put boots on the ground in Yemen in order to reopen the Red Sea to Israeli shipping suggests that America has little appetite for going to war on Israel’s behalf—and that is before taking into account the isolationism of the incoming Trump Administration.

Faced with what would amount to a global revolt against her sponsorship of genocide in the Middle East, America would flinch, potentially without a shot being fired.

Were an American failure to curb Israel to force an international coalition to put boots on the ground in Palestine, however, the coalition should not stop with the imposition of a ceasefire. Israel could be expected to break any ceasefire at the first opportunity given the Zionist aspiration to eradicate Palestinian life throughout Palestine.

Any coalition force should seek instead to impose a permanent peace in Palestine before withdrawing. But that could only be achieved through decolonization.

Consistent with international practice in more than eighty cases since 1945, the international community would withdraw recognition from Israel—the only settler state remaining anywhere in Africa or the Middle East—and aid the State of Palestine in gaining control over Palestine from the Jordan River to the Mediterranean sea.

Throughout history, powerful leaders have claimed to act according to rules. But it has only been when the community has banded together to enforce the rules against the powerful that law as we understand it today has come into being. Magna Carta was born in precisely that way.

The American-backed genocide that Israel is currently carrying out is a horror. But it is also a unique opportunity for the world to experience its first real constitutional moment.

For that to happen, however, the international community must prepare for war.

Ramsi A. Woodcock teaches international law and antitrust at University of Kentucky’s Rosenberg College of Law.