UB served mainly in the Mediterranean. In eight wartime patrols she sank 40 ships totaling 72, gross register tons GRT and one escort. Handed over to the United Kingdom on 16 January , she was broken up in Swansea in Hans von Mellenthin. UB could carry a crew of up to 34 men and had a cruising range of 9, nautical miles 16, km; 10, mi. UB had a displacement of t long tons while surfaced and t long tons when submerged.
Her engines enabled her to travel at Before breaking through the Strait of Gibraltar, UB sank six ships, damaging one further. While Spanish authorities planned to intern UB for the duration of the war, her crew managed to repair the damage to the fuel tanks and bunker enough oil to reach Cattaro. On 6 October , UB slipped out of the harbour and reached Cattaro nine days later with no fuel left. After refuelling UB sailed for Pola where the boat was repaired.
Already on the first day, UB was attacked by an enemy submarine. The next day, two Italian sailing ships were sunk, while exchanging fire with a coastal battery at the same time. On 15 December , UB managed to sink three steamers out of a convoy leaving Genoa, followed by two more the next day.
On 22 December , another two steamers were hit by torpedoes of UB The last torpedo on this cruise UB used on a British steamer off Naples. On the way back to Cattaro, UB experienced problems with her ballast tanks east of Malta and dived uncontrolled to a depth of 67 metres ft. Using compressed air to blow out all ballast tanks simultaneously, UB was able to surface again and continue her journey to Cattaro.
From 13 March UB pursued a convoy leaving Genoa for Naples and in two days managed to sink three out of four steamers. Between 19 and 21 March , UB operated in the Gulf of Naples , sinking several Italian sailing ships and shelling the fortifications of Civitavecchia.
