During the Polish-Bolshevik War the Pinsk Marshes in modern Belarus proved to be almost impassable to troops of both sides. Lack of roads and railways posed a serious danger to infantry and cavalry that could easily be cut off both by the enemy and the weather. Because of that, a number of river monitors were either constructed or acquired from private owners and armed. They were used on the Pripiat River, as well as its extensive river basin. After the war, some of the ships were returned to their owners, the rest remained on active service and were pressed into the so-called Pinsk Flotilla.