Submarine Campaign Submarine warfare in the Black Sea in World War II during 1944 involved engagements between submarines of the Soviet Black Sea Fleet attacking Axis merchantmen, defended by Romanian and German naval warships, as well as German U-boats and Romanian submarines attacking Soviet merchants on the eastern Black Sea.

Before the conclusion of the campaign, Romania joined the Allies after King Michael's Coup.

It also inherited five CB-class midget submarines left by Italy, however only two of them were operable by July 1944 and were not used in offensive action.

The German anti-submarine capabilities in 1944 effectively neutralized the threat of Soviet submarines in the Black Sea.

[29] On the other hand, a combination of heavy Soviet anti-submarine actions prevented the 2 newly built Romanian submarines to achieve successes, while the 30th U-boat Flotilla was effectively eliminated by the combined effect of an air raid on Costanta on 20 August and the following King Michael's Coup (negating the survived U-boats a safe harbor and forcing their scuttling).