Listen to the podcast A History of the World in Spy Objects - James Grime: Engima Machine

U-571 is a powerful film that follows a US Navy submarine crew on a secret WWII mission to capture a German Enigma code machine from a disabled German U-boat.

Matthew McConaughey and Harvey Keitel lead the Battle-of-the-Atlantic thriller in a gripping chase between destroyer and submarine based on a true story - except, the movie is fiction. Director Jonathan Mostow reinvented history and enraged some Britons along the way.

The US Navy did capture the German submarine U-505 and two Enigma machines on June 4, 1944, though. So what’s the fuss all about? SPYSCAPE took a deep dive into the drama behind the scenes.
‍

‍
U-505: The Hunter Becomes the Hunted‍

In the final years of WWII, the US Navy created military formations to hunt German U-boats. Hunter-Killer Task Group 22.3, for example, consisted of a small aircraft carrier escort named the USS Guadalcanal (CVE-60) and five light destroyer escorts.

Guadalcanal was commanded by Captain Daniel V. Gallery - a former Olympic wrestler who flew Spitfires during the Battle of Britain. Gallery accessed the Top-Secret 10th Fleet, the US Navy's anti-submarine intelligence command in D.C. Inside the U-boat tracking room, codenamed F-21, Gallery learned the classified details of German U-boats, enhancing the mission's intelligence power. Gallery knew that a successful capture hinged on the Germans believing the sub was sunk, however. His team would need to maintain absolute secrecy about the capture.

The pivotal moment came on June 4, 1944, as Germany’s U-505 sub cruised off West Africa on the prowl for American and Allied ships. U-505 was a familiar and fearful name but on this day, the dynamics shifted. The German predator found itself in the surprising role of the prey. Under fire by depth charges from destroyer escort Chatelain and two F4F ‘Wildcat’ aircraft, U-505 surfaced and surrendered.

It was a historic capture. It had been more than a century since any US naval force boarded and captured an enemy vessel at sea. The German crew of 58 were captured, eventually transferred to a PoW camp in Louisiana, and segregated.
‍

U-505 and the Enigma‍

The Germans assumed submarine U-505 was sunk and made no major changes in naval Enigma. The Enigma was a type of encryption machine used by the Germans to encode WWII military communications. It had rotating wheels and plugboard connections, creating complex codes for each letter.

The Dutch developed the machine to communicate banking secrets and the Germans bought the patent in 1923 for intelligence. Poland then bought an Enigma at a trade fair and procured a codebook from a French agent. The Enigma’s settings offered 150,000,000,000,000,000,000 possible solutions, but the Allies, especially at Bletchley Park in the UK, had successfully deciphered these codes, helping to turn the tide of the war.

The Intelligence haul from the U-505 sub matched - and perhaps even exceeded - the intelligence haul from the previous captures of submarines U-110 and U-559, Clay Blair writes in Hitler's U-Boat War.
‍

‍

The intelligence haul

While some downplay the U-505 cache, OP20G chief Joseph Wenger said the cryptographic 'benefits' of U-505 included the Atlantic and Indian Ocean U-boat cipher keys for June 1944. With these keys, the US could read that traffic as soon as the Germans did and no Bombe time was required to decipher Enigma codes. The net gain was 13,000 Bombe hours, allowing the Allies to obtain new solutions that would have otherwise not been possible, Wenger wrote.

Ciphers recovered

Two ciphers were also recovered - the 'extremely important' current grid-chart - or geographic location - cipher, the first time one was ever physically compromised. And the 'Reserve Short Signal' cipher, which was to go into effect on July 15, 1944.

Crucially, U-505's secret papers referred to a 'Short-Signal Procedure Kurier’. All hands involved with Enigma-breaking kept a sharp lookout for further Kurier Information or procedures, a radically new comms system introduced into German U-boat operations, Wenger said.

The British war of words‍

The premiere of the movie U-571 in 2000 brought the decades-old war story into the mainstream media: ‘Hollywood's Worst Historical Errors’, the Daily Mail sneered. ‘U-571: You give historical films a bad name,’ The Guardian claimed. Even the UK Parliament damned the movie as an affront to the real sailors.

The British media gleefully pointed out the movie’s errors, among them that the Allies had several Enigma machines and rotors by 1940 and that HMS Bulldog captured the first naval Enigma decoder from U-110 in the North Atlantic in 1941.

Enigma was deciphered seven months before the US even entered WWII. The ‘Yanks’, Britain sniffed, seemed to base the movie’s ‘true story’ on Britain’s 1941 Operation Primrose involving HMS Bulldog and the triumph of recovering the codebooks. Case closed? Not quite.
‍

Busting the Bletchley Park Myth‍

While Alan Turing and his team of cryptologists are often credited with breaking the Enigma code, Bletchley wasn’t solely responsible. Polish mathematicians including Marian Rejewski, French intelligence, and Swedish mathematician Arne Beurling worked in combination with the Norwegian Intelligence Service and Bletchley while Ireland’s Emily Anderson and librarian Dr. Richard Hayes also cracked Nazi codes.

OP-20-G, the US Navy cryptanalysis group led by Wenger also intercepted and decrypted naval communications from Japanese, German, and Italian Navies.

And in early February 1941 on a wet, dark evening at Bletchley Park, America’s top-secret ‘Sinkov Mission’ arrived at Britain’s wartime code-breaking center under team leader Captain Abraham Sinkov, a former Brooklyn math teacher. Author Michael Smith, in The Real Special Relationship, said the top-secret visit marked the start of a collaboration between the two countries that endures to this day.
‍