After work up trials in Holy Loch, Unbroken went out to join the 10th Flotilla at Malta, with a work-up patrol from Gibraltar.
 She would spend most of her wartime career in the Mediterranean.
 She landed saboteurs under the command of Captain Peter Churchill at Antibes in the south of France.
 She then proceeded to Malta to reform the 10th Flotilla in June 1942.
 She was the only submarine operating from Malta until United, Unruffled and Unrivalled joined.
She took part in Operations Harpoon and Vigorous, in June 1942.
In July 1942, Unbroken attacked the main west coast railway line on the Italian mainland, and succeeded in blocking the line for 24 hours.
However, she received return fire from coastal artillery and sustained a hit on the battery, forcing her to return to Malta.
She was badly damaged in October 1942, by a counter-attack by Italian escorts after hitting a tanker, and was again repaired at Malta.

During her time in the Mediterranean, she sank the Italian merchants Edda and Bologna (the former French Monaco), the Italian pilot vessel F 20 / Enrica, and the Italian auxiliary minesweeper No.
17/Milano.
 She also damaged the Italian sailing vessel Vale Formoso II, the German (former Norwegian) tanker Regina, and most significantly, the Italian heavy cruiser Bolzano and the Italian light cruiser Muzio Attendolo during Operation Pedestal.
 Bolzano was hit in her oil tanks and set ablaze; she had to be beached at Panarea island; the Attendolo lost sixty feet of bow.
 Bolzano was out of action for the rest of the war.

Unbroken also attacked the Italian merchant Algerino, but missed her with her torpedoes.
 She later damaged the Italian merchant Titania, north-west of Tripoli, Libya.
Titania was taken in tow by the Italian destroyer Ascari.
Titania was sunk early the next day by HMS Safari.
 Unbroken returned to the UK in December 1943.

Unbroken was transferred on loan to the Soviet Union on 26 June 1944, where she was renamed V-2.
Sailing under Soviet flag she sank the German submarine chaser UJ-1220 on 12 October 1944.
She spent four years in Soviet service before being returned to the Royal Navy in 1949.
 She was scrapped at Gateshead from 9 May 1950.
After work up trials in Holy Loch, Unbroken went out to join the 10th Flotilla at Malta, with a work-up patrol from Gibraltar.  She would spend most of her wartime career in the Mediterranean.  She landed saboteurs under the command of Captain Peter Churchill at Antibes in the south of France.  She then proceeded to Malta to reform the 10th Flotilla in June 1942.  She was the only submarine operating from Malta until United, Unruffled and Unrivalled joined. She took part in Operations Harpoon and Vigorous, in June 1942. In July 1942, Unbroken attacked the main west coast railway line on the Italian mainland, and succeeded in blocking the line for 24 hours. However, she received return fire from coastal artillery and sustained a hit on the battery, forcing her to return to Malta. She was badly damaged in October 1942, by a counter-attack by Italian escorts after hitting a tanker, and was again repaired at Malta.
During her time in the Mediterranean, she sank the Italian merchants Edda and Bologna (the former French Monaco), the Italian pilot vessel F 20 / Enrica, and the Italian auxiliary minesweeper No. 17/Milano.  She also damaged the Italian sailing vessel Vale Formoso II, the German (former Norwegian) tanker Regina, and most significantly, the Italian heavy cruiser Bolzano and the Italian light cruiser Muzio Attendolo during Operation Pedestal.  Bolzano was hit in her oil tanks and set ablaze; she had to be beached at Panarea island; the Attendolo lost sixty feet of bow.  Bolzano was out of action for the rest of the war.
Unbroken also attacked the Italian merchant Algerino, but missed her with her torpedoes.  She later damaged the Italian merchant Titania, north-west of Tripoli, Libya. Titania was taken in tow by the Italian destroyer Ascari. Titania was sunk early the next day by HMS Safari.  Unbroken returned to the UK in December 1943.
Unbroken was transferred on loan to the Soviet Union on 26 June 1944, where she was renamed V-2. Sailing under Soviet flag she sank the German submarine chaser UJ-1220 on 12 October 1944. She spent four years in Soviet service before being returned to the Royal Navy in 1949.  She was scrapped at Gateshead from 9 May 1950.
HMS Unbroken