International Law and Peace Among Nations For almost a century, international law has tried to prevent interstate armed conflict—war among nations. The system is far from perfect, but empirical measures suggest significant success, particularly by reducing conflict over territory. Today, international law’s prohibition on the use of force is under pressure from all sides, including from the doctrine of “humanitarian intervention” used to justify President Trump’s airstrikes in Syria; territorial disputes including those in Ukraine and the South China Sea; the so-called “Thucydides Trap” created by China’s rise in global power; and the overall weakening of international law more generally, in part through human rights. A look at the actions of China, Russia, and the United States over the past several years will illustrate the growing threat to peace among nations—and also the opportunities available to strengthen international law in order to reduce this threat. Ingrid Brunk Wuerth is a leading scholar of foreign affairs and public international law. She serves as the Helen Strong Curry Chair in International Law and director of the International Legal Studies Program at Vanderbilt University. Professor Wuerth’s work has appeared in the Harvard, Chicago, Michigan, Northwestern, and Texas law reviews, among numerous other publications. She is a member of the board of editors of the American Journal of International Law and of the Lawfare blog and is a reporter for the Restatement (Fourth) of the Foreign Relations Law of the United States.