American aircraft attacked Rabaul, New Guinea according to the U.S. Joint Intelligence Committee. Daily summary dated 9 April 1942

An item reported that six US bombers attacked the harbour of Rabaul, New Guinea scoring a probably direct hit and 3 near misses on a large transport, and near misses on a probable cruiser and another transport.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 120 dated 9 April 1942