Taking advantage of the change of ruler, Prince Leo I of Galicia, after entering into a war with the Black Sea Tatars, led by Nogai Khan at that time, set out in 1280 onto the Lublin land, which could be invaded by plunderers, or in order to conquer it.

[3] At the head of 6,000 troops, aided by Tatars and princes Mstislav Danilowicz [pl] of Lutsk and Vladimir Vasilkovich of Volhynia, he crossed the border near Chełm.

He began the siege of Sandomierz, but most forces crossed the Vistula south of the city, heading for the Cistercian abbey in Koprzywnica.

At the same time, Vladimir Vasilkovich ordered his troops to attack Osiek (one of the Russian chronicles provides information about rich loot and prisoners captured in this city).

On March 7, the Polish knights, led by Leszek II the Black, launched a retaliatory expedition that approached Lviv.