When the Japanese attacked Pearl Harbor on the morning of 7 December, "Astoria" was some west of Hawaii steaming toward Midway with TF 12. At 0900 the following day, the heavy cruiser , flagship of Vice Admiral Wilson Brown, Commander, Scouting Force, joined up with TF 12, and Brown assumed command. Its ferry mission canceled, TF 12 spent the next few days searching an area to the southwest of Oahu, "with instructions to intercept and destroy any enemy ship in the vicinity of Pearl Harbor..."