The Type IXC U-166 was commissioned into the German Navy (Kriegsmarine) in March 1942, during the Second World War. After completing training with the 4th U-boat Flotilla, it joined the 10th U-boat Flotilla for active duty. The submarine’s initial operations were near the British Isles, after which it moved to France and then crossed the Atlantic to patrol the Gulf of Mexico.
During its brief service, U-166 was responsible for sinking four ships: the Dominican sailing vessel Carmen, the SS Oneida, the Gertrude FV, and the SS Robert E. Lee (1924). The attack on the Robert E. Lee would ultimately lead to the submarine’s destruction.
On July 30, 1942, U-166 torpedoed the Robert E. Lee just south of the Mississippi River Delta, sinking it. In response, the ship’s escort, the submarine chaser PC-566, launched a counteroffensive. Its commander, Lt. Cmdr. Herbert G. Claudius, reported that his crew had successfully destroyed the U-boat with depth charges. However, his claims were initially met with skepticism by Navy officials. Instead of receiving recognition, Claudius was reassigned to an anti-submarine warfare school.
On the same day, a U.S. Coast Guard Grumman J4F-1 Widgeon spotted a German U-boat off the coast of Louisiana. The crew reported attacking the submarine and claimed they had hit it. Despite this, U-166 and its 52 crew members were declared missing, though no U-boat was recovered after the assault.
The wreck of U-166 remained hidden until 2001, when researchers discovered the sunken remains of the Robert E. Lee, located less than two miles from the site of the attack. Using sonar, they identified the U-boat 6,650 feet beneath the surface. While partially buried in silt, the U-boat’s conning tower and deck gun were still visible.
As the remains of the crew were still inside, U-166 was designated a war grave.
In 2014, a survey of the submarine revealed significant damage to its forward section. Historians believe that a depth charge hit the forward deck, likely causing the submarine’s torpedoes to detonate, leading to its sinking.
As a result of this new information, it was determined that PC-566 had actually been responsible for the U-boat’s loss. Claudius was posthumously awarded the Legion of Merit with Combat “V,” with then-Secretary of the Navy Ray Mabus saying, “Seventy years later, we now know that [Claudius’s] report after the action was absolutely correct. [Claudius’s ship] did sink that U-boat, and it’s never too late to set the record straight.”
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U-166 holds the distinction of being the only U-boat to have ever been lost in the Gulf of Mexico.