Two cases, almost eighty years apart, in which a weaker power—the Confederacy and imperial Japan—sought to achieve an end to the war before the United States could mobilize its material advantages and before the weaker side’s limited resources ran out provide useful insights into this western Pacific conundrum. Studying the failure of both challengers bears particular lessons for the United States in its potential conflict with China, in ways that studying our past victories against these adversaries cannot.