The Type VIIC/41 was the Kriegsmarine's late-war refinement of the workhorse U-boat that had nearly strangled Britain's Atlantic supply lines. Displacing 769 tonnes on the surface and 871 submerged, U-1109 measured 67.10 metres bow to stern with a pressure hull of 50.50 metres and a beam of 6.20. Twin Germaniawerft F46 diesels drove her at 17.7 knots on the surface; submerged on her SSW electric motors she could make 7.6. Her operating depth was 230 metres - deep enough that Allied depth charges struggled to reach her. She carried fourteen torpedoes, or 26 mines, and bristled with an 8.8 cm deck gun, a 3.7 cm flak gun, and two 2 cm anti-aircraft cannons. None of it mattered. Ordered in April 1942, laid down in October 1943, launched the following June and commissioned at the end of August 1944, she arrived in service just as the U-boat war was being lost.

Hoß took U-1109 out of Kristiansand on 22 March 1945. Technical problems forced her into Bergen on 6 April with no enemy vessels engaged. Her second war patrol began at Bergen on 17 April - by which point Berlin was a ruin, Hitler had eight days left, and the Atlantic was so thick with Allied aircraft and escort groups that the Type VIIC's chances of surfacing safely had dropped to almost nothing. She sank no ships. She was hunted but not caught. On 8 May Germany surrendered. Karl Donitz, briefly Reichsprasident, sent the recall signal to his remaining U-boat captains: surface, fly a black flag, proceed to the nearest Allied port. Hoß turned U-1109 toward Scotland. On 12 May 1945, she pulled into the long, sheltered anchorage of Loch Eriboll - the same loch where 33 other U-boats would soon surrender alongside her, in a quiet, anti-climactic end to the Battle of the Atlantic.

Of the 156 U-boats that surrendered intact at the war's end, 116 were marked for Operation Deadlight - a deliberate, methodical drowning of the German submarine fleet in deep water north-west of Ireland. The Royal Navy did not want them studied, salvaged, or recommissioned. U-1109 was transferred from Eriboll to Lisahally on the River Foyle on 31 May 1945, joined the queue, and on 6 January 1946 was towed out and torpedoed by a British submarine. She sank in about 175 metres of water. The boat that had been built to sink ships had instead been sunk, deliberately and without ceremony, by the Royal Navy she had once tried to fight. Her wreck lies on the Atlantic floor somewhere off the north Irish coast, intact enough that divers have located the broad outline of her hull.