Japanese invasion of French Indochina
In September–October 1940, the ship was based at Hainan Island to support the Japanese invasion of French Indochina. In February 1941, "Sōryū" moved to Taiwan to reinforce the blockade of southern China. Two months later, the 2nd Carrier Division was assigned to the First Air Fleet, or "Kido Butai", on 10 April. "Sōryū"s air group was detached in mid-July and transferred to Hainan Island to support the occupation of southern Indochina. "Sōryū" returned to Japan on 7 August and became flagship of the 2nd Division. She was relieved of that role on 22 September as she began a short refit that was completed on 24 October. The ship arrived at Kagoshima two days later and she resumed her former role as flagship of the Division.