If you were to ask historians to name the most foolish treaty ever signed, odds are good that they would name the Kellogg-Briand Pact of 1928. The pact, which was joined by 63 nations, outlawed war. Ending war is an absurdly ambitious goal. To think it could be done by treaty? Not just absurd but dangerously naïve.

And the critics would seem to be right. Just over a decade later, every nation that had joined the pact, with the exception of Ireland, was at war. Not only did the treaty fail to stop World War II but it also failed to stop the Korean War, the Arab-Israeli conflict, the Indo-Pakistani wars, the Vietnam War, the Yugoslav civil war and the current conflicts in Ukraine, Syria and Yemen.

But the critics are wrong. Though the pact may not have ended all war, it was highly effective in ending the main reason countries had gone to war: conquest. This claim is supported by an empirical analysis we recently conducted of all the known cases of territorial acquisition during military conflict from 1816 to the present.

First, some context. Before 1928, countries had the legal right to wage war. If one state claimed to be victimized by another, international law permitted it to use force to right the wrong. International law also gave countries the right of conquest, meaning they could benefit from war by keeping its spoils, territory and, in some cases, people. The right of conquest did not depend on whether the conqueror was in the right. As long as it claimed to have been a victim, no matter how flimsy its argument, the conqueror became the new legal sovereign. It’s easy to see how the right to wage war could be, and was, abused.