Japanese troop transports leaving Bako, Pescadores always escorted according to the U.S. Joint Intelligence Committee. Daily summary dated 4 April 1942

An item reported that as a result of the effectiveness of the operation by American submarines in the Western Pacific were the Japanese troop convoys from Bako, Pescadores going to the south always escorted.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 115 dated 4 April 1942