Japanese invasion of French Indochina
Following the Japanese ship-naming conventions for aircraft carriers, "Hiryū" was named "Flying Dragon". The ship was laid down at the Yokosuka Naval Arsenal on 8 July 1936, launched on 16 November 1937 and commissioned on 5 July 1939. She was assigned to the Second Carrier Division on 15 November. In September 1940, the ship's air group was transferred to Hainan Island to support the Japanese invasion of French Indochina. In February 1941, "Hiryū" supported the blockade of Southern China. Two months later, the 2nd Carrier Division, commanded by Rear Admiral Tamon Yamaguchi, was assigned to the First Air Fleet, or "Kido Butai", on 10 April. "Hiryū" returned to Japan on 7 August and began a short refit that was completed on 15 September. She became flagship of the Second Division from 22 September to 26 October while "Sōryū" was refitting.