Hickam Field contained the majority of Hawaii's air defence, but the fighters had been parked, wing-tip to wing-tip in order to protect them against sabotage. This proved to be a mistake when the Japanese attacked in 1941, destroying the majority of US air power in the first day. After Hawaii fell to the Japanese, it was converted into a major base for the Japanese Navy. When the US returned in 1943, Hickam Field became the prime air field for the Japanese, until their air power was wiped out. It was the last air field to fall to the US.