The Top Secret Tenth Fleet
The U.S. Navy knew that capturing a U-boat would require more than firepower. The mission also had to be backed by the power of intelligence.
When Task Group 21.12 returned from its second antisubmarine patrol in April 1944, Captain Gallery gained admittance to the 10th Fleet, code name for the U.S. navy's antisubmarine intelligence command in Washington, D.C. At the heart of the operation was F-21: the U-boat tracking room. There, Gallery met Commander Kenneth Knowles, who gave Gallery top-secret information about the inner workings of German U-boats.
Knowles and his 10th Fleet team had been tracking a target U-boat since March of 1944, when the sub cast off from Brest, France and headed south toward Africa. The exact identity of the U-boat was unknown, but Knowles determined it was probably an older sub with a three-month duration at sea. Task Group 22.3 would have until the end of May to capture the U-boat before it made its way home.