Kapitänleutnant Reinhard Hardegen and U-123 were on their second war patrol in U.S. waters hunting for targets of opportunity. On Mar. 30, 1942 the boat arrived off Cape Hatteras, North Carolina en route he sank three ships including USS Atik AK-101. Finding the waters off North Carolina too shallow for effective operations and a dangerous place for a submarine he moved further south to the coast of Georgia. Early in the morning on April 8, 1942 Hardegen was positioned off Brunswick, Georgia when in the darkness he made out the silhouettes of two tankers.

Oklahoma, a steam tanker built in 1940 by Sun Shipbuilding in Chester, Pennsylvania was en route from Port Arthur, Texas to Providence, Rhode Island carrying 66,000 barrels of kerosene, 30,000 barrels of gasoline and 4,000 barrels of diesel fuel, she was unarmed, unescorted and running a straight course. The ship was running without lights and maintaining radio silence with three lookouts on a clear night. At 0200 (E.W.T.) she was hit in the engine room by a single torpedo. An SOS was sent claiming that they had been in a collision and the ship was abandoned. However screams were heard from the ship and the master, Theron P. Davenport, 3rd Mate Malcolm MacPhee and Boatswain Henry Maahs (and perhaps a third man) reboarded the ship and found the mortally wounded 2nd Engineer trapped in his quarters. They managed to free him through the skylight, but were unable to save the eighteen others who were trapped inside the lower decks of the ship. A second SOS was sent and the ship was again abandoned.

Hardegen then moved his boat toward the Esso Baton Rouge, another steam tanker built in 1938 by Bethlehem Shipbuilding Corp., Sparrow's Point, Maryland for the Standard Oil Company. She was operating in much the same way as the Oklahoma, en route from Texas to the upper east coast (New York) carrying 70,000 barrels of lubricating oil and 20,000 gallons of heating oil), unarmed, unescorted, blacked out, radio silence, lookouts, but she was zigzagging. This however did not save her from the same fate as Oklahoma. A single torpedo hit her on the starboard side which set the ship ablaze and killed two crewmen. The ship settled by the stern which soon rested on the bottom only 40' below. The thirty-five survivors, including the master, James S. Poche, got off in the lifeboats, but one man, a naturalized German refused to get in and jumped overboard in a rubber suit, he was never seen again. A report surmised that he may have boarded the submarine, but there is no evidence to support this claim.

U-123 left the scene and returned to the Oklahoma and shelled the ship until she was also resting on the bottom and on fire. Hardegen then retired before a counterattack could be mounted against his boat. He sank five more ships before returning to France in early May.

Later the survivors claimed that there were two or even three submarines which attacked in a pack, and that the Germans taunted them after they were in the lifeboats, the former statement is of course incorrect, the latter statement can not be independently confirmed. Ten hours after the attacks the survivors were found by the Coast Guard and towed to safety at St. Simmon's Island, Georgia.

Both ships were raised and repaired and both would be lost to U-boats later in the war. Esso Baton Rouge was lost on Feb. 23, 1943 to U-202 and Oklahoma on Mar. 28, 1945 to U-532. Sadly more crewmen were also lost with them.