Unraveling the Mystery: The Discovery of the U-166

by Robert A. Church & Daniel J. Warren

Historic Background

Spring 1942; the war was going well for Nazi Germany as Hitler launched Operation Drumbeat. Using the might of Germany's Unterseeboote, the new operation would take the war to the coasts of America as his predecessors had done in World War I. Unlike the U-boats of World War I, however, this time they would not be limited to the east coast of the United States, but would extend their destruction to America's soft underbelly, the Gulf of Mexico (Miller, 2000: 6-17).

Hitler left the running of Operation Drumbeat to Admiral Dönitz, the commander of the Kriegsmarine, as the German Navy was known. In May 1942 with the sinking of the Norlindo by U-507, a wave of destruction began in the Gulf of Mexico that in just under 12 months would see 17 U-boats send 56 merchant vessels to the bottom and severely damage 14 others. Two of the vessels that fell victim to this onslaught were the cargo freighter Alcoa Puritan and the passenger freighter Robert E. Lee (Wiggins, 1995: passim).

Korvettenkapitän Harro Schacht, commanding U-507, was the first U-boat commander to enter the Gulf of Mexico. On May 6, 1942, Schacht sank his fourth ship in the Gulf. At 11:55, he attacked the Alcoa Puritan as she was en route from Port-of-Spain, Trinidad to Mobile, Alabama with a load of bauxite. The first torpedo missed and the alarm was sounded. The captain of the Alcoa immediately ordered full speed (about 16 knots) and turned his ship to present as small a target as possible to the U-boat. U-507 surfaced and began pursuit at about 18 knots, slowly overtaking the freighter. At a distance of about a mile, U-507 opened fire with both deck guns. Over the next forty minutes, the U-boat expended nearly seventy-five rounds, scoring approximately fifteen hits, and disabling the Alcoa Puritan's steerage. The captain brought the crippled freighter to a stop and gave orders to abandon ship. After all the crew made it off the freighter, U-507 moved in and finished the ship off with a torpedo. The Alcoa Puritan sank stern first in approximately eight minutes. The U-boat approached with 100 yards of the survivors and a German officer shouted through a megaphone, "Sorry we can't help you. Hope you get ashore." He then waved as U-507 sailed away. About 3 1/2 hours later the survivors were rescued by the U.S. Coast Guard cutter Boutwell (Browning, 1996: 96).

SS Robert E. Lee, January 20, 1942.
(5,184-ton, 375 ft. x 55 ft.)
Photo courtesy of the Mariners' Museum, Newport News, Virginia

A few months later, in July, the passenger freighter Robert E. Lee left Trinidad with limited cargo and approximately 270 passengers, many of whom were American construction workers or survivors of other U-boat attacks in the Caribbean. She carried approximately 131 crewmembers and 6 armed guards, who manned a deck gun mounted on the stern of the vessel. She came up through the Caribbean with a convoy, then continued into the Gulf of Mexico with a naval escort vessel, Patrol Craft 566. Lieutenant Commander H. C. Claudius was in command of PC-566. She was a newly commissioned vessel and her first mission was to escort the Robert E. Lee through the Gulf of Mexico (USS PS-566, 1942; and Henderson, 1942).

Late in the evening on July 29 they neared Tampa, Florida for a scheduled stop. The passengers asked Captain William C. Heath of the Robert E. Lee to allow them to disembark at Tampa to escape the miserable conditions on board the overcrowded freighter. Captain Heath agreed, but when a pilot was unavailable to guide the boat into the Tampa harbor he decided to continue on to their final destination of New Orleans, Louisiana. With the decision to continue to New Orleans the naval escort broke radio silence to notify the Gulf Sea Frontier command (the military command that oversaw wartime shipping activities in the Gulf of Mexico) that the Robert E. Lee was proceeding to New Orleans. The escort was ordered to continue with the Robert E. Lee. (Talbot-Booth, 1942: 1186; Wiggins, 1995: 138-39; and Browning, 1996: 194-95).

In July 1942 there were at least ten U-boats operating in the Gulf of Mexico. One of these was U-166, commanded by Hans-Günther Kühlmann. U-166 had been laying mines off the mouth of the Mississippi for several days. On July 27, 1942 Kühlmann radioed the German Subcommand that he had finished his mine laying operation. Although no further messages were received from Kühlmann after July 27 it is presumed that U-166 took up position to attack shipping coming into or out of the Mississippi River. On July 30th U-166 was prowling along the shipping lanes as the Robert E. Lee and PC-566 steamed toward New Orleans (War Diary, 1942: 36, 53, 92; and Garrison, 1989).

The skies were clear and the sea calm on the evening of July 30th as the Robert E. Lee neared the Mississippi River. Around 4:30 PM and only 45 miles from Southwest Pass the passengers must have been anticipating their arrival in New Orleans when a few of them saw something in the water streaking towards their vessel. They questioned each other as to whether it could be a shark or perhaps a dolphin, but it was a torpedo. The German "eel" slammed into the starboard side of the vessel, exploding just aft of the engine room. The ship began sinking quickly and many of the passengers and crew frantically donned life jackets then jumped overboard into the Gulf waters. Amidst the chaos, members of the crew managed to lower six lifeboats and sixteen life rafts that were quickly overloaded with survivors (Henderson, 1942).

The crew of the escort vessel, traveling approximately a half-mile ahead of the Robert E. Lee, had been radioing New Orleans for a pilot when the attack occurred. Immediately PC-566 went into action. The Patrol Craft raced to the area where they had last spotted a periscope and the crew dropped a spread of five depth charges. After coming about they gained sonar contact on the U-boat and maneuvered to drop another spread of depth charges. Upon coming around for the second attack, Lieutenant Commander Claudius noted that the Robert E. Lee had already disappeared beneath the water leaving only lifeboats and scattered debris to mark the location. It is estimated that the freighter sank within five to fifteen minutes of being hit. Following the escort's attack on the U-boat an oil slick was reported and no further signs of the U-boat were observed. Feeling that the U-boat was no longer a threat, the crew of PC-566 turned to the task of rescuing the survivors of the Robert E. Lee. (Henderson, 1942; and Wiggins, 1995: 140).

Soon search planes appeared overhead to help watch for the U-boat and direct other rescue vessels to the site. Just after 8:30 PM two additional vessels, SC-519 and the tugboat Underwriter, joined the rescue operation. The Underwriter had just arrived at the pilot station to reopen South Pass when the request came to help. Bar pilot Captain Albro Michell recalled the events:

South Pass was closed during the war and we had gone down to open it back up. We had just arrived at the pilot station when we were asked to go out and help in the rescue of a boat that had been torpedoed....We took about 50 to 60 passengers off the naval ship onto the Underwriter. The seas were dead calm, otherwise we would not have been able to transfer the victims. Someone was watching out for them... When we were asked go out we only knew a ship had been torpedoed. We still had the provisions onboard for the pilot station; we didn't have time to unload them. The survivors were hungry and ate all the provisions on the way into Venice (Michell, 2001).

The survivors were transported to Venice, Louisiana, then by bus and ambulance to the New Orleans hospital. As a result of the U-boat attack, 15 passengers and 10 crew were lost, including Winifred Grey of New Orleans, one of the few women merchant marines to be lost in wartime action in the Gulf of Mexico (

On August 1, two days after the Robert E. Lee was sunk, Coast Guard aviators Henry White and George Boggs were on patrol in their Grumman J4F seaplane out of Homa, Louisiana. At about 1:30 PM they spotted a German U-boat on the surface. Immediately they radioed their position south of Isles Dernieres, Louisiana and began an attack run on the enemy vessel. The U-boat initiated a crash dive and was quickly slipping beneath the surface. When the plane neared 250 feet, White yelled "NOW!" and Boggs released the charge. He reported seeing the charge detonate near the vessel and a light to medium oil slick appeared on the surface of the water. After returning to base White and Boggs were instructed that the incident was classified and not to speak of it further. At the end of the war they were told that it was the U-166 they had sunk that day (Wiggins, 1995: 142; "Baseball," 1943).

But was it? The entire premise that the U-166 was sunk that day in August is based entirely on the fact that the U-166 never returned from its war patrol and was never heard from again. No other evidence supports the claim. The last radio message from the U-166 was on July 27, 1942 three days before sinking the Robert E. Lee.

The area in which the U-166 is thought to have been sunk is probably one of the most surveyed regions in the world. Oil and gas development in the area have led to numerous intensive surveys using various means or remote sensing instruments. For decades individuals, companies, and governments have extensively searched the area for the U-166. In 1997 a team from Germany came to search for the U-boat, but no trace of the U-166 was identified (; and McNamara, 2000).

Oil and Gas Surveys

In 1986, Shell International Exploration & Production, Inc. was conducting oil and gas exploration in the Mississippi Canyon Area of the Gulf of Mexico. They contracted John Chance and Associates to conduct the survey using a 706 EDO deep-tow side scan sonar. While performing the survey they detected two shipwrecks, which they identified as the Robert E. Lee and the Alcoa Puritan. The two sunken vessels would remain identified as such for the next sixteen years.

In January 2001, C & C Technologies, Inc. (C & C) conducted a deep-water pipeline survey for British Petroleum (BP) Amoco and Shell International in the vicinity of the reported location of the Robert E. Lee and Alcoa Puritan. This survey was conducted using C & C's new HUGIN 3000 AUV (High Precision Untethered Geosurvey and Inspection System, Autonomous Underwater Vehicle). The HUGIN 3000 is the world's first commercially operated AUV capable of surveying to 3000 meters water depth. It is untethered, therefore it can operate even in rough seas at faster speeds with greater mobility and accuracy than conventional towed arrays. Operating in 5000 feet of water, C & C's AUV is accurate to within 9 feet after post processing. Conventional towed systems are typically only accurate to 100 or more feet at the same water depth. The AUV utilizes a state-of-the-art multibeam bathymetry and imagery system, a dual frequency chirp side scan sonar, chirp sub-bottom profiler, an inertial navigation system coupled with the precision HiPAP (High Precision Acoustic Positioning) acoustic tracking system.

During the January survey, a large shipwreck was detected at the edge of the AUV's survey corridor in 5000 feet of water. C & C Marine Archaeologists Robert A. Church and Daniel J. Warren contacted the United States Department of Interior, Minerals Management Service (MMS) to verify the identity of the vessel as the Robert E. Lee. C & C asked their clients if they could run a few investigation lines around the Robert E. Lee and the reported location of the Alcoa Puritan. BP and Shell not only responded favorably to the additional investigation, they decided to have C & C conduct a 2 mile by 1.5 mile investigation survey in the area to precisely position any wreckage or outlying debris of both shipwrecks. This survey was conducted in March 2001 and addressed the archaeological and engineering concerns of the companies. The investigation survey consisted of 17 survey lines at 492-foot (150 meter) line spacing for a total of 31.7 nautical line miles. Using the AUV the entire investigation survey took less than 9 hours to complete, a fraction of the 72 hours a conventional deep-towed system would have required.

Upon completion of the offshore work the data from the archaeological survey was reviewed by the C & C's marine archaeologists. As they began analyzing the data the archaeologists realized that the debris scatter formerly identified as the Alcoa Puritan did not match the characteristics of a 6,759-ton freighter. The target consisted of two large sonar contacts with debris of various size scattered between them. The largest section of debris measured approximately 200 feet long and 20 feet wide. The other large section measured approximately 55 feet long and 20 feet wide. This made a combined length of approximately 255 feet, just over half the length of the Alcoa Puritan, which was 397 feet long by 60 feet at beam. Based on this data, Church and Warren were doubtful the target was the Alcoa Puritan, but realized it did match closely the dimensions of a Type IX-C German U-boat (Length = 252 feet, Beam = 22 feet), as was the type of U-166.

A New Interpretation

The data from the AUV provided circumstantial evidence to support the U-166 hypothesis. But, it did not seem reasonable to locate the U-166 140 miles away from where it was reportedly bombed and within less than a mile of the U-boat's last victim. One possibility to explain the discrepancy was put forward by the archaeologists. What if the crew of the PC-566 were far luckier on July 30 than anyone had given them credit, and had actually sunk the U-166 instead of just chasing it off as was presumed? If this was the case then which U-boat was bombed by White and Boggs on August 1 and what happened to that vessel?

Further research revealed there were three U-boats operating in the Gulf of Mexico on August 1, 1942 (U-166, U-509, and U-171). U-166 sank in the Gulf of Mexico with no survivors. Only infrequent radio transmissions provide clues to U-166's activities in the Gulf of Mexico, but if it was sunk by PC-566 then the Coast Guard could not have attacked it two days later. U-509 did not venture very far into the Gulf and did not sink any shipping during that patrol. It arrived safely back in Lorient, France on September 12, 1942 with no incident mentioned of a seaplane attacking them on August 1. The only other boat known to remain in the Gulf at this time was the U-171 commanded by Günther Pfeffer (War Diary, 1942; and

U-171 arrived at its assigned area of operation between Galveston and New Orleans on July 23, 1942. Pfeffer's objective was to sink shipping coming into and out of the Port of Galveston. However, he found that the waters off Galveston were too shallow and radioed that he was moving toward the New Orleans area. Pfeffer found success off the Louisiana coast, sinking the R. M. Parker, Jr. on August 13, 1942. Curiously, the attack on the R. M. Parker, Jr. took place within three miles of the location that White and Boggs made their attack on a U-boat (Wiggins, 1995: 109-111). On October 9, 1942, while returning from their patrol in the Gulf of Mexico, U-171 struck a mine and sank in the Bay of Biscay. Pfeffer along with twenty-nine crewmen survived, but twenty-two crewmen and the Captain's logs went down with the vessel. In Pfeffer's reconstructed logs he mentioned that between July 27 and August 13, 1942 a "flying boat" had dropped one depth charge on them and they escaped with no damage (NARA, U-171). From this research the archaeologist surmised that White and Boggs bombed U-171 on August 1, 1942. It also seemed probable that the debris to the east of the Robert E. Lee was the remains of U-166, which PC-566 sank following the attack on the Robert E. Lee. According to the Action Report of PC-566, Lieutenant Commander Claudius and his Executive Officer, D. Howard felt they had sunk or severely crippled the U-boat. Furthermore Claudius stated that they "believed that the submarine was watching the sinking of the SS Robert E. Lee and was not aware of our [PC-566] presence." It was not until the U-boat heard the ping of the sonar that they began to dive. If U-166 was not expecting the naval escort, then it is doubtful the U-boat had overheard the radio transmission sent by PC-566 the previous day.

Further Investigations

With the new hypothesis, C & C informed their clients, BP and Shell, that they might have found the long sought after U-boat. C & C, BP, and Shell then held a meeting with the MMS to fully disclose the information. In light of the possibility of the new discovery, BP and Shell sponsored further site investigations of the Robert E. Lee, and the suspected U-166 site using the AUV. The additional investigation provided revealing sonar and bathymetry images and provided further evidence supporting the U-166 hypothesis. The conning tower and deck guns of a U-boat could clearly be recognized from the 410 kHz sonar images. The bathymetry data showed the U-boat was lying in what appeared to be a six-foot deep impact creator. Because of the possibility that the site represented a significant historical wreck, ground truthing was warranted with a Remotely Operated Vehicle (ROV) for final verification of the remains.

AUV 410kHz Side Scan Sonar Image
ROV survey

On May 31 and June 1, 2001 a research team from C & C, BP, Shell, and the MMS conducted an ROV survey of the SS Robert E. Lee and the suspected site of U-166. The archaeologists from C & C were joined by marine archaeologists Jack Irion and Richard Anuskiewicz of the MMS for the expedition. The research team left onboard the Garry Chouest, an anchor-handling vessel on contract to Shell, which was equipped with Oceaneering's Millennium VI ROV. After reaching the site it took a hour to lower the ROV to the seafloor. The researchers set up about 200 feet south of the U-boat and slowly moved the ROV across the seafloor toward the wreck site. The first image of the U-boat was the side of the conning tower looming out of the darkness.

The conning tower and stern appear to be intact and in good order. This section is deeply imbedded in the seafloor, only revealing the top of the deck, conning tower and deck guns. The conning tower is in excellent condition with the splashguard and railing of the wintergarten showing little or no damage. The 105mm deck gun, 37mm and 20mm antiaircraft guns are in place and clearly visible. The teak decking that once covered the deck frame is no longer present, having likely been eaten away by biological organisms.

After completing a thorough investigation of the stern section and conning tower, the research team relocated the ROV to the separated bow section, which lies 490 feet to the west-northwest. The bow section provided a revealing glimpse of what caused the U-boat to plummet to the seafloor. Just forward of where the forward torpedo-loading hatch would have been located, a large indentation is visible in the deck. This damage appears to be the result of a depth charge explosion. The jagged metal where the bow tore away from the rest of the vessel is flared outward as if caused by an internal explosion. The evidence observed at the bow suggests a depth charge exploded almost right on top of the deck, rupturing the pressure hull. That event in turn caused an internal explosion, possibly from an armed torpedo or from salt water rushing into the battery room, both of which were present in that location of the U-boat. There is a large amount of scatted debris between the two sections of the U-boat, including what appear to possibly be two torpedoes partially protruding from the seafloor.

The ROV was then moved over to the site of the Robert E. Lee. As the stern of the vessel came into view there was no doubt we were looking at the passenger freighter. The ROV maneuvered around the entanglements of the structure, collecting detailed video images of the final resting place of the Robert E. Lee. The deck gun on the stern was seen, which the eight man gun crew manned. Two lifeboats were videoed lying off to the port side of the ship. A large scatter of debris surrounds the freighter and while exploring the debris field an unexpected discovery was made in the late hours of the survey. About 1:00 in the morning we moved the ROV toward a piece of debris lying over 200 feet off the port side of the Robert E. Lee. The first thing that came into view as we approached the unknown debris was a bit of metal framing lying on the seafloor. Then as the camera panned around, there stood the telegraph off the bridge of the Robert E. Lee. It was an unbelievable find, just standing all alone on the seafloor just as if it were still on the bridge. Made of brass, it was in pristine condition and the words on the face of the telegraph could still be read. The indicator arrow from the engine room was locked in the "STOP" position, indicating the "All Stop" command was sent and executed before the ship went down. The handle, however, was pulled back into the "FINISHED WITH ENGINES" position, a command that was never executed. This left the researchers to speculate that as the ship was sinking the bridge officer possibly pulled the handle back to that position out habit before leaving the bridge.

Bridge Telegraph of the SS Robert E. Lee as found on the Seafloor, June 1, 2001

The new technology of the AUV, the historical research, and the combined efforts of the expedition team, positively identified the final resting-place of the Robert E. Lee and the U-166, solving one of the great historical mysteries of World War II in the Gulf of Mexico. On July 30, 1942, 25 lives were lost from the Robert E. Lee and 52 German sailors from the U-boat. As the news of the discovery spread to the surviving family members it helped bring some closure to questions gone unanswered and some vindication for the crew of PC-566 over credit never given. One of the unique elements of this archaeological site is that it tells the whole story of the U-boat war in the Gulf of Mexico. The hunter, U-166; its last victim, the Robert E. Lee; and the lifeboats representing the survivors are all found within a mile from each other on the seafloor. Now history has been rewritten and the story set straight with the discovery of U-166.

Select Bibliography

Browning, Robert M., Jr. U.S. Merchant Vessel War Casualties of World War II. Annapolis: Naval Institute Press, 1996.

"Baseball Cap Strikes Out Sub," The Key West Citizen, Gainsville, FL., June 18, 1943.

Garrison, Ervin G., C. P. Giammona, F. J. Kelly, A. R. Tripp, and G. A. Wolff. Historic Shipwrecks and Magnetic Anomalies of the Northern Gulf of Mexico: Reevaluation of Archeological Resource Management Zone 1. Volume II: Technical Narrative. OCS Study 89-0024. U. S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office. New Orleans, Louisiana, 1989.

McNamara, Dave. "Thunder in the Gulf: Nazi subs torpedoed ships off the Louisiana coast, and at least one paid the price." Louisiana Life (Summer, 2000):

Michell, Albro. Interview by Robert Church over the Phone, August 14, 2001, and at Captain Michell's, New Orleans, Louisiana, August 24, 2001.

Miller, David. U-Boats: History, Development and Equipment, 1914-1945. London: Conway Maritime Press, 2000.

National Archives and Records Administration (NARA). Records of the German Navy, 1850-1954: Records Relating to the U-boat Warfare, 1939-1945. Compiled by Timothy Mulligan. Washington, D.C.: United States National Archives, 1985.

Henderson, E. D. Summary of Statements by Survivors of the SS Robert E. Lee, U.S. Cargo-passenger vessel, Navy department, Office of the Chief of Naval Operations, Washington, August 15, 1942.

Talbot-Booth, E. C. Ed. Merchant Ships, 1942. New York: The MacMillan Company, 1943.

"Women Mariners in World War II," U.S. Merchant Marine, June 5, 2000.

War action casualties involving merchant tank vessels. Prepared by Merchant Vessel Inspection Division, U.S. Coast Guard. [n.d.] U.S.C.G. Washington D.C.

War Diary. Oberkommando Kriegsmarine Kriegstagebuch, Akten betreffend U-166, from March 24, 1942 through August 3, 1942. NARA, Washington DC. English translation in C J. Christ's personal archives, Houma, LA.

Wiggins, Melanie. Torpedoes in the Gulf, Galveston and the U-boats, 1942-1943. College Station: Texas A&M Press, 1995.

This article was published on 29 Mar 2002.

Torpedoes in the Gulf

Wiggins, Melanie

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