From commissioning until late 1941 the first six "Sargo"s were based first at San Diego, later at Pearl Harbor. The last four were sent to the Philippines shortly after commissioning. In October 1941, the remaining "Sargo"s and most other newer available submarines were transferred to the Asiatic Fleet in the Philippines as part of a belated effort to reinforce U.S. and Allied forces in Southeast Asia. The Japanese occupation of southern Indo-China and the August 1941 American-British-Dutch retaliatory oil embargo had raised international tensions.