Akagi was an aircraft carrier built for the Imperial Japanese Navy (IJN), named after Mount Akagi in present-day Gunma Prefecture. Though she was laid down as an Amagi-class battlecruiser, Akagi was converted to an aircraft carrier while still under construction to comply with the terms of the Washington Naval Treaty. The ship was rebuilt from 1935 to 1938 with her original three flight decks consolidated into a single enlarged flight deck and an island superstructure.

Akagi’s aircraft served in the Second Sino-Japanese War in the late 1930s. Upon the formation of the First Air Fleet in early 1941, she became its flagship, and remained so for the duration of her service. With other fleet carriers, she took part in the Attack on Pearl Harbor in December 1941 and the invasion of Rabaul in the Southwest Pacific in January 1942. The following month, her aircraft bombed Darwin, Australia, and assisted in the conquest of the Dutch East Indies. In March and April 1942, Akagi’s aircraft helped sink a British heavy cruiser and an Australian destroyer in the Indian Ocean Raid.