On 26 June 1941, shortly after the Axis invasion of the Soviet Union (Operation Barbarossa), "Regina Maria" helped repel a Soviet naval attack against the main Romanian port of Constanța, together with the flotilla leader "Mărăști". The Romanians were expecting an attack and the accuracy of their fire, reinforced by the heavy guns of the German coastal artillery battery "Tirpitz", caused the Soviet ships to withdraw, losing the destroyer leader in a Romanian minefield that had been laid shortly before the start of the war. Her sister ship was lightly damaged by one of the Romanian ships and the heavy cruiser "Voroshilov" was slightly damaged by a Romanian mine as the Soviets were withdrawing.