Danube Delta Campaign

The Danube Delta Campaign was a series of naval engagements between the Soviet Danube Flotilla and its Romanian counterpart in late June 1941, during the first days of Operation Barbarossa.

Background
After annexing Bessarabia and Northern Bukovina from Romania in the summer of 1940, the Soviet Union gained a border on the Danube. The Soviets created a new flotilla on the Danube, which was formed of ships transferred from the Dnieper Flotilla. The new Danube Flotilla consisted of five monitors (armed with 102 mm and 130 mm guns), twenty-two armored boats, and five transports, supported by an anti-aircraft battalion, fighter and bomber squadrons, a rifle company, a machine gun company, a naval infantry company, and eight shore batteries (two 152 mm, one 130 mm, one 122 mm, one 76 mm, and three 45 mm gun batteries).

Romania joined Operation Barbarossa and declared war on the Soviet Union on 22 June 1941, launching attacks against Soviet airfields in Bessarabia and destroying numerous aircraft on the ground.

The engagements
The first Soviet-Romanian naval engagement occurred on 22 June 1941, the first day of Operation Barbarossa, when one Soviet monitor and one patrol boat attacked the port-city of Tulcea. The Romanian river monitors Basarabia and the Brătianu-class NMS Mihail Kogălniceanu repulsed the attack, sinking the patrol boat.

The main naval engagement on the Danube occurred on the following day, when the Romanian Tulcea Tactical Group (Basarabia, Mihail Kogălniceanu and four patrol boats) repelled another attack of the Soviet Danube Flotilla, damaging two monitors and two patrol boats and one tug. The Romanian monitors then counterattacked at Reni, sinking one patrol boat and one barge and damaging another Soviet monitor.

The last naval engagement on the Danube occurred on 26 June, when two Romanian patrol boats, V1 and V3, engaged three Soviet patrol boats, setting one of them on fire and forcing all three to retreat.

Aftermath
Despite these defeats, the Soviet Danube Flotilla continued to support ground forces in bridgeheads and landing operations, and also fought numerous artillery duels with the Romanian Land Forces during and in the days prior to Operation Munchen.

The Romanian monitors also fought against the Red Army troops, shelling Soviet artillery positions near Giurgiulești on 8 and 14 July.