SM UB-123
SM UB-123 was a German Type UB III submarine (U-boat) of the Imperial Navy in World War I. Built by AG Weser in Bremen (yard 296), she was laid down on 13 July 1917, launched on 2 March 1918 and commissioned on 6 April 1918 under Oblt.z.S. Robert Ramm. She served with the III Flotilla for two patrols.
UB-123 had a displacement of 512 tons surfaced and 643 tons submerged, was 55.85 meters long, with a beam of 5.80 meters and a draught of 3.72 meters. She was powered by two Körting diesel engines (1,050 bhp) and two Siemens-Schuckert electric motors (780 shp), allowing 13.9 knots on the surface and 7.6 knots underwater. Her range was 7,280 nautical miles at 6 knots on the surface and 55 nautical miles at 4 knots submerged. Test depth was 50 meters. She carried a crew of 3 officers and 31 men and was armed with five 50 cm torpedo tubes (ten torpedoes) and one 10.5 cm deck gun.
During two patrols, UB-123 sank one merchant ship of 2,646 GRT, damaged another of 4,095 GRT, and took three merchant ships as prizes (3,530 GRT).
On 10 October 1918 UB-123 torpedoed and sank Leinster, a vessel near Dublin, with over 500 lives lost—the worst maritime disaster in the Irish Sea. On 19 October 1918, UB-123 struck a mine from the North Sea Mine Barrage and sank; all 36 crew were killed.
This page was last edited on 3 February 2026, at 16:03 (CET).