 Kaga entered the shipyard on 15 December 1938, where her arrester gear was replaced by a Type 3 system and her bridge was modernized. The flight deck and hangar areas were enlarged, increasing the carrier's aircraft capacity. The ship was completely overhauled from 15 November 1939 to 15 November 1940 before returning to active service. In the meantime, a new generation of aircraft had entered service and Kaga embarked 12 Mitsubishi A5M fighters, 24 Aichi D1A dive bombers and 36 Yokosuka B4Y torpedo bombers. Another 18 aircraft were carried in crates as spares.
