A true war-horse entered the area next in the form of U-107 which was put through thirteen patrols by four skippers (starting with Hessler and Gelhaus), and sank or damaged 42 ships of nearly a quarter of a million tons. She operated in fifteen wolf-packs against convoys and had a total of 743 days at sea on war patrol. To arrive off the Bahamas the boat was attacked in Biscay by a Halifax bomber but was undamaged after the boat counter-attacked with its deck guns (Wynn, Vol. 1, p.90).
The Type IXB boat’s tenth patrol, under Volker Simmermacher took it to the coast off South Carolina for a week out of its 68 day total patrol, and then back again along a similar route northeast of the Bahamas. Entering south of Bermuda, U-107 steamed west from the 18th to the 20th of August 1943, at which point it swung northwest and exited the region on the border of South Carolina on about the 24th. During its patrol off the Carolinas it damaged two ships – the Albert Gallatin, a US steamer of 7,176 tons and the large Navy oiler, USS Rapidan (AO 18) via mine on the 11th of September 1943 for a total of 15,422 tons.
Returning southwards via the Georgia coast after a week of mine-laying operations and patrols, the U-boat then headed east-southeast between the 1st and 4th of September before taking a one-day detour due south during the 5th. Resuming its eastward trend on the 6th, U-107 exited the area on the 8th in the same position as she entered: south of Bermuda. She had spent just shy of three weeks in the region and was bound from and to Lorient, where it was based with the Second Flotilla. The patrol lasted from 28 July to the 3rd of October 1943.
Volker Simmermacher was Oberleutnant zur See at the time and became Kapitänleutnant in 1944. A member of Crew A of 1937, he accumulated three patrols on U-107 for 197 days – this was his first on the boat. He damaged one other ship in his career, the US warship Lark of 148 tons, for a total damaged of 15,570. He neither sank an enemy ship nor was awarded any decorations over his career. He lived until 1990 and the age of 80.
U-107 was one of the boats fitted with an advanced Schnorchel device, enabling it to ventilate and recharge the batteries from under water and reducing the vulnerable surface time required of it. Nevertheless the boat was sunk with all hands on the 18th of August 1944 west of La Rochelle France by a Royal Air Force Sunderland aircraft.
SOURCES: Gudmundur Helgason, Rainer Kolbicz, www.uboat.net, 2011, Kenneth Wynn, U-boat Operations of the Second World War, Volume 1 and Volume 2, 1997