The Oituz participated in several Axis convoys to the Bosporus and to the Crimea. She was slightly damaged by a Soviet submarine in December 1941 near the Turkish-Bulgarian border. Between 28 March and 10 Apr 1944, the ship took part in the evacuation of Odessa and made three voyages, evacuating a total of 2100 soldiers. In May 1944, Oituz went to Sevastopol and evacuated 700 soldiers to Constanza on 14 May. 

At 03.31 hours on 1 Sep 1944, U-23 fired three torpedoes into the harbour of Constanza and reported three detonations after running times of 1 minute 46 seconds. Two hits were observed at the berth of a Romanian Regele Ferdinand type destroyer and one hit on a steamer of 6000 tons. However, only the already damaged Oituz was hit by one torpedo in the stern and sank at her moorings at berth #22, while another torpedo detonated at the wall in the empty berth #23. She was later refloated and declared a total loss.

The U-boat left her attack position at 04.00 hours and laid one EMS mine in the roads near Tuzla lighthouse, but apparently without success.