Following King Michael's Coup, where Romania switched sides and joined the Allies in late 1944, the two ships were seized and incorporated into the Soviet Black Sea Fleet.

[5] They could carry 480 long tons (490 t) of fuel oil[3] which gave them a range of 3,000 nautical miles (5,600 km; 3,500 mi) at a speed of 15 knots (28 km/h; 17 mph).

[11] Massively outnumbered by the Soviet Black Sea Fleet, the Romanian ships were kept behind the minefields defending Constanța for the next several months, training for the convoy escort mission that would be their primary task for the rest of the war.

Beginning on 5 October, the Romanians began laying minefields to defend the route between the Bosphorus and Constanța; the minelayers were protected by the destroyers.

[Note 2][13][14] During the winter of 1941–1942, the Romanian destroyers were primarily occupied with escorting convoys between the Bosporus and Constanța, and then, after the ice melted in April 1942, to Ochakov and Odessa.

Regina Maria and Regele Ferdinand also escorted the minelayers as they laid defensive minefields to protect the convoy routes in 1942–1943.

[12][13][15] Successful Soviet attacks in early 1944 cut the overland connection of the Crimea with the rest of Ukraine and encircled Axis troops in Sevastopol during April.

After the 5,700-gross register ton (GRT) cargo ship SS Alba Iulia was bombed and set on fire by Soviet aircraft on 18 April, the sisters were dispatched to see if she could be salvaged.

They put a skeleton crew aboard to operate her pumps and to stabilise her before a pair of tugboats arrived the next morning to tow her to Constanța.

[16] After the capitulation of Romania to the Soviet Union in August 1944, the sisters were seized and incorporated into the Black Sea Fleet as Likhoy (Лихой, ex-Regele Ferdinand) and Letuchiy (Летучий, ex-Regina Maria).