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Military + EspionageMilitary & Espionage

Discovering U-Boat 166

Hitler’s U-Boats sank 609 allied ships in American-protected waters during WWII. More than 5,000 lives were lost and over 3 million tons of cargo never reached its destination, as Hitler attempted to disrupt the crucial flow of supplies from America to Britain. The allies managed to sink only ten of these U-boats in American-protected waters during the war and only one in the Gulf of Mexcio—U-Boat 166. However, the circumstances surrounding U-boat 166’s sinking resulted in decades of controversy.

Discovering U-Boat 166


In July of 1942, a cargo ship named the Robert E. Lee was attacked and sunk in the Gulf by a U-boat torpedo. The ship’s naval escort,

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PC-566, launched a counter attack. The commanding officer, after observing an oil slick on the water’s surface, claimed to have successfully sunk the U-boat. However, instead of being commended, Captain Herbert Claudius was believed to have botched the attack and removed from command. Credit for sinking U-boat 166 was instead given to a Coast Guard patrol plane in an attack two days later and 140 miles to the west. Yet no U-boat was ever found after the Coast Guard attack

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In the summer of 2001, two marine archeologists with C&C Technologies—Dan Warren and Rob Church—were conducting a pipeline survey in the Gulf Coast of Mexico. They had expected they might come across the wreckage of a cargo freighter, the Alcoa Puritan, but instead found the remains of lost German U-boat 166, unraveling a nearly 60-year-old maritime mystery and vindicating Captain Herbert Claudius.

Sunken Nazi U-boat, U-166
Conning Tower from wrecked Nazi U-boat, U-166
© Ocean Exploration Trust

Dan Warren:  It wasn’t a planned mission to go out and search for a U-boat. There was no set scientific expedition in 2001. We were doing a survey that was part of our normal job, a pipeline survey. And it just so happens, Rob had an interest in the U-166 since he came on at C&C, and we always kind of looked at data just in case.

"That’s when it started to click that—what’s going on here?"

And when we started looking through the data, we were expecting to see the remains of a 6,000-ton tanker [the Alcoa Puritan], and what we actually saw was a much smaller target that did not match what I was expecting to see. That’s when it started to click that—what’s going on here? I started thinking about what Rob had told me. It’s [U-166] going to be somewhat of a cigar-shaped target, and that’s when I wrote and I copied the photo, the sonar record, and put it on the desk because I knew this was something. Now, whether it would turn out to be the U-166, I didn’t know at that time.

Rob Church:  At that point, I took the schematic of a type IX U-boat and made an overlay of it and printed it out on transparency at the same scale as the sonar image that we had. When I slid the two together, the details matched up perfectly. So, at that point we knew it was a 90% deal that we had the U-166.

Basically for nearly 60 years, recorded history indicated that the U-boat was sunk 140 miles to the west up on the shelf. Now we’re looking at it in deep water—then we had to try to explain why it’s there. 

Marine archeologists Dan Warren and Rob Church
Marine archeologists Dan Warren and Rob Church with C&C Technologies
© WGBH Educational Foundation


In an effort to uncover what had actually taken place almost 60 years earlier, Rob Church then pored over German U-boat logs from the war. He found a log from the Captain of U-171, which was eventually sunk off France after leaving the Gulf of Mexico. The Captain said that on or about August 1, they had been bombed by a “flying boat”—an apt description of the Coast Guard aircraft that had been credited for sinking U-166. Rob Church and Dan Warren realized they had the missing piece of the puzzle, and that two different U-boats had been involved in the attacks in the Gulf.

Church:  People had been looking for this boat for years. For almost 60 years this U-boat had been missing somewhere out in the Gulf of Mexico. So when we looked at this and [it] really started to sink in that we may have found it, that was a little overwhelming really, and it was exciting.

“Discovery is not an event, it’s a process.”

Warren:  It was kind of unbelievable—we didn’t believe we could get this lucky. To not only come across the U-boat on the sea floor, but be able to come up and find the supporting documentation in the historical record and really have a rare moment that very few archaeologists or historians have of changing what is written in the history books.

Church:  As is most often the case, and it was the case with U-166, discovery is not an event, it’s a process, and this was definitely a process, and it involved not just two young archaeologists that got lucky, but it was a team of folks— the people that went out and collected the data, the surveyors, the technicians, the engineers, the managers that planned those surveys.


Editor's Notes

As a result of Warren and Church’s discovery and further research conducted by explorer Bob Ballard, Commander Claudius was posthumously awarded the Legion of Merit by the U.S. Navy. For the full story on the sinking of U-boat 166, watch “Nazi Attack on America.”

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