Answer
The attack on Pearl Harbor on December 7, 1941, profoundly impacted Admiral William D. Leahy's career, prompting his recall to active duty. This momentous event, often regarded as a catalyst for the United States' entry into World War II, drew Leahy back into service as the Chief of Naval Operations. His expertise and experience proved invaluable in shaping the nation's military strategy and navigating the complexities of the global conflict.