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U Boats in the Gulf of Mexico: Torpedoed Tankers and the Oil Supply during WWII

Updated: Jul 16, 2019

On May 5, 1942, the German submarine U-507 sank two tankers, the Munger T. Ball and the Cudahy, in the Gulf of Mexico west of the Florida Everglades. The ships were the first tankers to be sunk by U Boats in the Gulf of Mexico, and part of a total of 100 that were lost to German submarines in the Caribbean and the Gulf of Mexico. Two months later, on July 8, 1942, the tanker J. A. Moffett was sunk in the Florida Keys, about 5 miles south of Duck Key. A map of all the attack locations (based on data from in the Gulf of Mexico shows a band from Key West and the Dry Tortugas northwest toward the mouth of the Mississippi River. The U Boats targeted tankers at their origin in the Mississippi River, and when they transited the choke point of the Florida Straits between Key West and Cuba. This brought some of the attacks relatively close to the Florida shoreline south of Tampa and west of Everglades City.

The U Boats were based in Lorient, France, where the Germans set up a base after the conquest of that country. With a distance of 5000 miles one way from Lorient to the Gulf of Mexico, the round trip was equivalent to traveling almost halfway around the world. The submarines were able to make the voyage and still have a capacity to raid Allied shipping by the use of specialized supply submarines, which allowed the U Boats to obtain diesel fuel and provisions on extended cruises.

The magnitude of the loss of oil caused by these attacks can be estimated from the capacity of the sunken tankers. The gross tonnage of the 100 tankers attacked and sunk was 742,272 gross tons, according to Hitler’s U Boat War by Clay Blair. This would equal over 13 million barrels of oil if the ships were full, which most were. If you like to think in gallons, this would be 546 million gallons. That is the total production expected from a medium sized oil field. The effect of the released oil on the Gulf and the coastal areas where it eventually came ashore must have been devastating, but few scientific assessments, if any, are available. The population of the coastal areas in the 1940s was much smaller than today, and there were few resources to dedicate to environmental issues during wartime. Perhaps core samples taken today in the marshes and reefs of Louisiana, the Everglades and the Keys, age calibrated by carbon 14 dating, could detect evidence of oil contamination and related damage preserved in the geologic record.

The main impact of the tanker sinkings to the Allies, however, was not the loss of the oil but a disruption to the petroleum supply chain. In 1942 and 1943, crude oil was transported from the oil fields in Texas and Louisiana to the refineries in the northeastern US, near New York City and Philadelphia. Transformed to gasoline and diesel fuel, it was shipped to Europe as a vital component of the war effort. The U Boat attacks on the tankers blocked the flow of raw material (crude oil) to the refineries, precipitating a critical shortfall.

Harold Ickes - 32nd U.S. Secretary of the Interior

In 1942, President Franklin Roosevelt appointed Harold Ickes, the Secretary of the Interior, as the Petroleum Coordinator for War. His role was to coordinate the efforts of federal and state agencies, as well as industry, to ensure adequate supplies for military operations as well as domestic needs. This required increasing oil production to meet the needs of the US and Britain, as well as solving the problem of transporting crude oil from Texas and Louisiana to New York and Delaware. The effort resulted in increased exploration and production, as well as pipeline construction to transport the oil overland, safe from the U Boat attacks. US oil production from 3.7 million barrels a day in 1940 to 4.7 million barrels a day in 1945, sufficient to meet the needs of the country and provide the needed fuel for the war. New fields were discovered across the country, including Texas, Louisiana, Michigan, and Florida. The discovery of the Sunniland Field in south Florida, which plays a prominent role in my novel Sunniland, had the additional benefit of access to the Intracoastal Waterway along the East coast of the US, protected from the U Boat threat.

By the end of 1943, the US Navy had succeeded in stopping the U Boat attacks, and pipelines had replaced tankers as the primary means of moving crude oil from Texas to the New Jersey. Three U Boats are known to be on the seafloor of the Gulf of Mexico, sunk by depth charges. They are the U-166 southeast of the South Pass of the Mississippi River, the U-157 south of Key West, and the U-176 in the Florida Straits. The U-166 was discovered in 2001 by a remotely operated submarine from an oilfield vessel, an endeavor in which I participated. The discovery voyage of the U-166 will be the subject of a separate post.

Most of us of us fortunate enough to live in the United States have always thought of World War II as battles fought overseas, in places like Normandy, Guadalcanal, and Okinawa, far from the lower 48 states. But the map at the beginning of this post shows that in 1942 or 1943, combat operations with loss of life on both sides took place within a relatively short distance of Key West, Naples, and New Orleans.


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U Boats, Oil Exploration and life in the Everglades during WWII in my new novel Sunniland.

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