Japanese believed that all Allied warships except for submarine left their waters according to the U.S. Joint Intelligence Committee. Daily summary dated 20 March 1942

An item reported that the Japanese believed that their extensive air reconnaissance patrolling pointed out that except for submarines all Allied warships left the Japanese waters.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 100 dated 20 March 1942