Enemy submarines active on the North Atlantic Ocean according to the U.S. Joint Intelligence Committee Daily summary dated 13 May 1942

An item reported that in the night 11-12 May probably three enemy submarines attacked a 40 ships numbering westbound North Atlantic convoy on a distance of 800 miles north by west of the Azores and torpedoed 5 ships. It was believed that the submarines still shadowed the convoy. This was the first serious attack on a North Atlantic convoy in a while.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 154 dated 13 May 1942.