Four months after the Pearl Harbor attacks, Kapitanleutnant Reinhard Hardegen decided that Americans should see for themselves what war with Adolf Hitler's Germany was going to look like.

He began with Florida sunbathers. On April 11, 1942, Hardegen's submarine, U-123, torpedoed the tanker SS Gulfamerica off Jacksonville. He maneuvered U-123 around the flaming wreck and surfaced between the SS Gulfamerica and the beach. He sank it with U-123's deck gun.

Hardegen later wrote in his log: "All the vacationers had seen an impressive special performance at [President Franklin D.] Roosevelt's expense. A burning tanker, artillery fire, the silhouette of a U-boat -- how often had that been seen in America?"

Hardegen was one of the few "Unterseeboot" commanders to survive the war. Most did not, as the U.S. turned to the convoy system and sonar to devastate the "wolfpacks" and keep open the supply lines to Britain.

He claimed he was never a Nazi.

"I did my duty for my country, not for Hitler," he reportedly said.

He was believed to be the last surviving U-boat commander when he died on June 9 at age 105.

Christian Weber, president of the state parliament in Bremen, Hardegen's hometown, confirmed the death to local media, but did not provide the circumstances.

Hardegen's bravado off the Jacksonville coast nearly cost him his boat and his life, according to the bestseller "Operation Drumbeat: The Dramatic True Story of Germany's First U-Boat Attacks Along the American Coast in World War II," by historian Michael Gannon.

The roads to the beach became jammed with people eager to see the cruel spectacle. Nineteen crew members of the SS Gulfamerica had been killed, and beachgoers scrambled into rowboats to rescue survivors.

Hardegen lingered too long and was forced to crash dive to the bottom at a depth of only 66 feet to avoid approaching U.S. patrol aircraft.

The destroyer Dahlgren dropped a pattern of six depth charges, heavily damaging U-123. Hardegen ordered the crew into escape gear and prepared to abandon his boat, but he froze in fear as he was about to open the conning tower hatch.

The Dahlgren did not keep up the attack. U-123 had survived. Hardegen later told Gannon, "only because I was too scared was I not captured."

Upon his return to Germany, Hardegen was awarded oak leaves to his Knight's Cross and, along with Erich Topp, another of Germany's "aces of the deep" U-boat commanders, had dinner with Hitler. Hardegen reportedly claimed he told Hitler that he was neglecting the submarine service and focusing too much attention on the Eastern Front.

Hitler was infuriated and ordered Gen. Alfred Jodl, chief of the operations staff, to issue Hardegen a reprimand.

"The Führer has a right to hear the truth, and I have a duty to speak it," Hardegen responded, according to accounts.

Later, as a korvettenkapitan, Hardegen was in charge of training units. Near the end of the war, he was made a battalion commander of a ground unit.

When the war ended, he was jailed by the British when he was mistaken for an SS officer with the same last name. He returned to Germany, took up golf, and became a successful businessman for an oil company. Ironically, he had dealings with Texaco, whose ships he sank in World War II.

Hardegen came to the U.S. following the publication of "Operation Drumbeat."

He told the Atlanta Journal-Constitution that, "now I sink putts, not ships."

Hardegen and U-123 were credited with sinking 22 ships, a total of more than 115,000 gross register tons, in two war patrols off the East Coast as part of Operation Drumbeat.The operation was the plan of Admiral Karl Dönitz, commander of the Germany's submarine service, to disrupt allied shipping and demoralize the American homefront.

On his first war patrol in January 1942, Hardegen surfaced at night in U-123 in the mouth of New York Harbor. The U.S. had yet to begin ordering blackouts along the coast.

He and his crew could see the lights of the Wonder Wheel, the big ferris wheel at Coney Island. They could see the Manhattan skyline aglow. The sights were familiar to Hardegen. As a cadet in 1933, he had visited the city and went to the top of the Empire State building.

The U-123 could not find any targets in the harbor but later attacked shipping off Long Island.

"I cannot describe the feeling in words," Hardegen later wrote in a memoir of his venture into New York harbor, "but it was unbelievably beautiful and great."

"We were the first to be here," he wrote, "and for the first time in this war a German soldier looked out upon the coast of the U.S.A."

-- Richard Sisk can be reached at Richard.Sisk@Military.com.