Van Allen was commissioned as a U.S. Navy lieutenant in November 1942 and served for 16 months on a succession of South Pacific Fleet destroyers, instructing gunnery officers and conducting tests on his artillery fuses. He was an assistant staff gunnery officer on the battleship USS Washington when the ship successfully defended itself against a Japanese kamikaze attack during the Battle of the Philippine Sea, (June 19–20, 1944). For his actions at the Pacific, Van Allen was awarded four battle stars. He was promoted to lieutenant commander in 1946. "My service as a naval officer was, far and away, the most broadening experience of my lifetime," he wrote in a 1990 autobiographical essay.