First patrol

On 16 July 1942 U-511 sailed from Kiel and across the Atlantic to the Caribbean Sea.

At 06:29 on 27 August, U-511 fired a spread of four torpedoes at Convoy TAW-15, en route from Trinidad to Key West, about 120 nautical miles (220 km; 140 mi) south-south-east of Guantánamo Bay in Cuba, sinking two ships and damaging another.^[6] The 13,031 GRT British tanker San Fabian, loaded with 18,000 tons of fuel oil, was hit and sunk. The master, 31 crewmen and one gunner were picked up by the destroyer USS Lea and the patrol craft PC-38, 23 crew members and three gunners were lost.^[7] The 8,968 GRT Dutch tanker Rotterdam, carrying 11,364 tons of gasoline was struck and immediately began to settle by the stern. The 37 survivors of her crew of 47 abandoned the ship in lifeboats and were picked up by USS SC-522.^[8] The 8,773 GRT American tanker Esso Aruba, loaded with 104,170 barrels (16,562 m³) of diesel fuel and serving as the flagship of the convoy commodore, was hit by a single torpedo on the port side which badly damaged the ship, but left the engines and steering gear still operating. This allowed the ship, in danger of breaking in two, to proceed under her own power to Guantánamo Bay, arriving the next day. The ship was beached and her cargo unloaded. After temporary repairs the ship proceeded to Galveston, Texas, and was returned to service in February 1943.^[9]

The U-boat arrived at her new home port of Lorient in occupied France, on 29 September after a voyage lasting 76 days.^[2]

Second patrol

U-511 sailed from Lorient on 24 October 1942, and patrolled the waters off the coast of north-west Africa before returning to base after 36 days, on 28 November, having had no successes.^[10]

Third patrol

U-511, now under the command of Oberleutnant zur See Fritz Schneewind, left Lorient once more on 31 December 1942 to patrol the waters between Spain, the Canary Islands and the Azores.^[11] At 21:42 on 9 January 1943 she had her only success, sinking the 5,004 GRT British merchant ship William Wilberforce, loaded with 5,054 tons of West African produce, including palm kernels, palm oil and rubber en route from Lagos to Liverpool. The unescorted ship was torpedoed west of the Canary Islands, with the loss of three crewmen. The master, 41 crewmen, six gunners and 12 passengers were later picked up by the Spanish merchant ship Monte Arnabal.^[12]

U-511 returned to Lorient on 8 March after 68 days at sea.^[2]

Fourth patrol

U-511's final patrol took her all the way to Japan, as part of the ongoing programme of technological exchange. She had aboard additional personnel, including Ernst Woermann, the German ambassador to the pro-Japanese Wang Jingwei regime in China, Vice Admiral Naokuni Nomura, the Japanese naval attaché in Berlin, and German scientists and engineers. Leaving Lorient on 10 May 1943 under the command of the now Kapitänleutnant Fritz Schneewind, she sailed through the Atlantic and around the Cape of Good Hope into the Indian Ocean where she made two kills.^[13][14]

The first attack was made at 09:42 on 27 June, when she hit the unescorted 7,194 GRT American Liberty ship Sebastian Cermeno with two torpedoes, disabling the engines and killing an officer and two men. The survivors abandoned ship in five lifeboats. Ten minutes after being hit, the ship sank. The U-boat surfaced and questioned the survivors before leaving. The lifeboats lost contact with each other, but all were eventually rescued by Allied ships, apart from one boat which made its own way to Madagascar.^[15] Her second success came on 9 July when she torpedoed the 7,176 GRT American Liberty ship Samuel Heintzelman, loaded with 5,644 tons of ammunition and general cargo. The U-boat dived after firing and did not directly observe the results, but heard underwater explosions. On surfacing they saw no trace of the ship, only floating debris. There were no survivors from the 75 men on board. The ship was reported missing, and was at first believed to have been sunk by a Japanese surface raider. On 30 September, wreckage from the ship was discovered off the Maldives.^[16]

The U-boat arrived at Kure on 7 August after a voyage lasting 90 days^[2] and was handed over to Japan on 16 September.^[1]

Japanese service

After being commissioned in the Imperial Japanese Navy as Ro-500, in September 1943 it was examined by a team of Japanese naval engineers. Several elements of the Type IXC design were later incorporated into the I-201-class. The boat's German crew trained Japanese personnel in its handling, then departed for Penang in late September. Starting in November 1943, Ro-500 was assigned to the Naval Submarine School at Ōtake as a training ship.^[4]

In May 1944, Ro-500 was assigned to Submarine Division 33 along with Ro-62, Ro-63, and Ro-64. That month Ro-500 participated in testing anti-submarine warfare equipment with dive bombers from the 634th Naval Air Group. From July 1944 to May 1945, it was used for training purposes in the Kure Naval District, before being reassigned to the 51st Squadron along with Ro-68 and sent from Kure to the Maizuru naval base.^[17] For the rest of the war, Ro-500 was at Maizuru to help train air crews in anti-submarine warfare by simulating an American submarine. After Japan's surrender, the crew of Ro-500, led by Lieutenant Yasuhisa Yamamoto, joined the rebels that wanted to continue the war against the Soviets. They departed from Maizuru on 18 August 1945, but the 6th Fleet headquarters contacted the crew, and the same day Ro-500 returned to Maizuru.^[4]

Fate

Ro-500 was scuttled in the Gulf of Maizuru along with the Japanese submarines I-121 and Ro-68 by the United States Navy on 30 April 1946.^[1][14]

In 2018, an expedition led by the Society La Plongee for Deep Sea Technology discovered the wrecks of Ro-500 and I-121 in Wakasa Bay off the coast of Kyoto Prefecture.^[18]