Originally laid down as a second Sōryū-class carrier, Hiryū underwent several significant design changes during construction, resulting in her being designated as her own class. The ship was widened to improve stability, she received a higher bow to improve sea keeping, the hull was strengthened, and the island shifted to the port side, making Hiryū one of only two aircraft carriers to have one to date. Commissioned in July, 1939, Hiryū joined Sōryū in the 2nd Carrier Division, covering the invasion of French Indochina in 1940, and supporting the blockade of southern China in 1941. Hiryū underwent a brief refit in August and September, before joining the attack on Pearl Harbor. Her aircraft inflicted heavy damage, and were most likely responsible for the bomb hit that set off the battleship USS Arazona's magazine. On the way home, Hiryū joined Sōryū in covering the invasion of Wake Island, before returning to Japan to replenish. In the new year, Hiryū ventured South with the other carriers, supporting the invasion of the Dutch East Indies and raiding Darwin, Australia, before deploying to the Indian Ocean in April. After mauling the British forces in the region, Hiryū returned to Japan for a brief refit. She joined the attack on Midway Island, and Hiryū's air group commander led the combined carrier strike on the island, when Akagi's was hospitalized with appendicitis. Hiryū escaped the morning ambush that incapacitated the other three carriers, having become separated during the numerous American air attacks over the morning. Hiryū launched two counter attacks that fatally crippled the American carrier USS Yorktown, but was herself taken out of action by Yorktown dive bombers flying from the carrier USS Enterprise. Hiryū was scuttled early the next morning, but thirty-nine of her crew were left behind, entering the carrier's cutter to be picked up by the Americans several days later, after four had died of their wounds or exposure.