Activities of the enemy submarines in the Atlantic theatre according to the U.S. Joint Intelligence Committee. Daily summary dated 23 December 1941

An item reported that there had been no recent contacts with enemy submarines off the Atlantic coast and very few were located over the northern trade routes. There seemed to be 10-16 submarines between the Azores and Portugal destined to the north. The J.I.C. commented that many of these submarines had been active well south of the Cape Verdes. It was possible that their supplyer was lost forced them to return home. Furthermore is discounted the reported presence of a submarine base in the C. Verdes or Canaries.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 13 dated 23 December 1941.