😱How U.S. Defeated Japan in World War II CONTEXT: How did the United States manage to defeat Japan during World War II? While Nazi Germany was expanding in Europe, its ally Imperial Japan was conquering territories across Asia. In 1941, Japan launched a surprise attack on Pearl Harbor in Hawaii, crippling part of the U.S. Navy and starting the Pacific War. For a short time, Japan had the upper hand. But the Battle of Midway (1942) changed everything. In just four days, the United States destroy