German Submarine U-505 - Outcome

Outcome

The cipher materials captured on U-505 included the special "coordinate" code, the regular and Offizier Enigma settings for June 1944, the current short weather codebook, the short signal codebook and bigram tables due to come into effect in July and August respectively.

The material from U-505 arrived at the decryption establishment at Bletchley Park on 20 June 1944. While the Allies were able to break most Enigma settings by intense cryptanalysis (including heavy use of the electromechanical "bombes"), having the Enigma settings for the U-boats saved a lot of work and time, which could be applied to other keys. The settings break was only valid until the end of June and therefore had an extremely limited outcome on the eventual cracking of the enigma code, but having the weather and short signal codebooks and bigram tables made the work easier.

The "coordinate" code was used in German messages as an added layer of security for actual locations. Its capture allowed Allied cryptanalysts to determine more precise locations for U-boat operating areas. Allied commanders sent Hunter-Killer task groups to these known U-boat locations, and routed shipping away.

A more lasting benefit came from the intact capture of the U-boat's two G7es (Zaunkönig T-5) acoustic homing torpedoes. These were thoroughly analyzed and then tested on the range, giving information that was invaluable in improving the Foxer and FXR countermeasures systems, as well as the doctrine for using them to protect escorts.

That U-505 was captured and towed—rather than merely sunk after the codebooks had been taken—was considered to have endangered the Ultra secret. The U.S. Chief of Naval Operations, Admiral King, considered court-martialling Captain Gallery. To protect the secret, U-505's crewmen, who knew of the U-boat's capture, were isolated from other prisoners of war; the Red Cross were denied access to them. Ultimately, the Kriegsmarine declared the crew dead and informed the families to that effect. The last of the German crew was not returned until 1947.

For leading the boarding party, LTJG Albert David received the Medal of Honor, the only time it was awarded to an Atlantic Fleet sailor in World War II. Torpedoman's Mate Third Class Arthur W. Knispel and Radioman Second Class Stanley E. Wdowiak, the first two to follow David into the submarine, received the Navy Cross. Seaman First Class Earnest James Beaver, also of the boarding party, received the Silver Star. Commander Trosino received the Legion of Merit. Captain Gallery, who had conceived and executed the operation, received the Navy Distinguished Service Medal.

The Task Group was awarded the Presidential Unit Citation. Admiral Royal E. Ingersoll, Commander in Chief, U.S. Atlantic Fleet, cited the Task Group for "outstanding performance during anti-submarine operations in the eastern Atlantic on 4 June 1944, when the Task Group attacked, boarded, and captured the German submarine U-505 … The Task Group's brilliant achievement in disabling, capturing, and towing to a United States base a modern enemy man-of-war taken in combat on the high seas is a feat unprecedented in individual and group bravery, execution, and accomplishment in the Naval History of the United States."

U-505 was kept at the navy base in Bermuda and intensively studied by U.S. Navy intelligence and engineering officers. Some of what was learned was included in postwar diesel submarine designs. To maintain the illusion that she had been sunk rather than captured, she was temporarily renamed USS Nemo.