The Bolshevik assault started on 26 May, with the aim of cutting off the Polish 2nd and 3rd Armies and encircling them in a huge pocket.

One of the assaulting divisions of the Cavalry Army, the Soviet 11th Cavalry Division, managed to break the front line between the two Polish armies and assaulted a fortified village of Bystrzyk, defended only by a single infantry company of the Polish 50th Kresy Rifles Regiment.

The following day, the Russian division expanded the gap, broke through to the other side of the front and managed to drive approximately 15 kilometres towards the rear of the Polish forces.

The commander of the Polish 6th Army, Gen. Wacław Iwaszkiewicz, ordered a counter-assault group to be created out of all available reserves.

Although the forces of both sides were more or less equal, the surprise was decisive and the Russians sounded a retreat after a short skirmish.