Very shortly after Poland regained independence, in April 1919, the Pinsk Flotilla was formed, which from 1931 was called the Navy River Flotilla (abbreviated as MW). This flotilla, as indicated by its second name, which is organisationally subject to the Polish Navy, was responsible for patrol and surveillance activities as well as cooperation with land forces in the eastern borderlands of the Second Polish Republic, and more specifically on the Pripyat, Pina and Strumień rivers. The flotilla actively participated in the Polish-Bolshevik war (1919-1939), taking part in the conquest of Mazyr, and later in the Kiev expedition (1920). However, in August 1920, in the face of the impending Soviet offensive, the Flotilla was disbanded, but was reactivated for service in 1922. Three years later, it became the only river flotilla in the Polish Navy. The main base of the flotilla was Pinsk, where there were flotilla barracks, all administrative buildings, a port of things and - in the years 1928-1937 - a seaplane base. In 1939, the Flotilla consisted of the headquarters, three combat squadrons, a mine and gas department, a communications department, a technical emergency service and the administration of the naval port in Pinsk. The flotilla took part in the battles of the September campaign, but during the campaign, the crews of the ships sank virtually all of its units so that they would not fall into enemy hands.