By May of 1942 U-boats had been ordered into the Gulf of Mexico by Dönitz as an extension of Operation Paukenschlag (Drumbeat). The first two boats who made it to the Gulf were U-506 and U-507, followed shortly thereafter by U-753. U-506 was commanded by Kapitänleutnant Erich Würdemann, he was the boat's only commander and this was the first war patrol for both.

The boats entered the Gulf in early May 1942 and by May 11 were off the mouth of the Mississippi River and New Orleans cruising for the easy victims who were not expecting an attack. Shipping in the Gulf at that time was not escorted, but some were armed, such was the case of the SS David McKelvy.

The tanker David McKelvy was built in 1921 by Sun Shipbuilding in Chester, Pennsylvania, and on May 14, 1942 was en route from Corpus Christi, Texas to New York with 80,000 barrels of crude oil when she was found by U-506. Würdemann fired only one torpedo at the unescorted ship, but that was enough to cause the cargo to explode and the ship to break amidships.

According to the survivors there was no panic and all but two men abandoned the ship within 20 minutes, the two who remained stayed in the fresh water tanks until the flames burned out and were picked up the next day by a Norwegian tanker. The derelict ship was reboarded on May 29, towed to the Louisiana coast and beached, it was declared a total loss.

The 23 men who had survived were picked up by the Coast Guard ship Burwell WPC-130 and taken to Burwood, Louisiana where one died of his wounds. The explosion and resulting fire claimed the lives of sixteen men who were some of the first victims of the U-boat war in the Gulf. The McKelvy was not the first ship attacked in the Gulf, nor was it the last, both U-506 and U-507 claimed several other victims before departing the Gulf on May 20.

When Würdemann returned from his patrol he was awarded the Eisernes Kreuz 1. Klasse (Iron Cross 1st Class) and would later be awarded the Ritterkreuz des Eisernen Kreuz (Knight's Cross of the Iron Cross), but he would not have much time to enjoy his award. While outbound from Lorient to the African coast on his 5th war patrol his boat was located by a U.S.A.A.F. B-24 Liberator on July 12, 1943, depth charged and sunk, Würdemann was not among the six survivors.