A lot of nations of the Holy Roman Empire saw the Thirty Years' War as a perfect opportunity to (re)gain their independencies. One of them was Hungary led by Gábor Bethlen, Prince of Transylvania. He joined Bohemia in the anti-Habsburg Protestant Union. In a short period of time, he conquered northern Hungary and Bratislava, and in November he started a siege of Vienna - the capital city of Austria and the Holy Roman Empire. The situation of Emperor Ferdinand II was dramatic. The emperor sent a letter to Sigismund III of Poland, and asked him to cut the supply lines of Bethlen from Transylvania. He also sent
George Drugeth, count of Homonna - former rival of Bethlen, now Lord Chief Justice of Royal Hungary - to Poland, to hire forces for the Habsburgs.
The Polish-Lithuanian Commonwealth did not want to participate in the war, so it remained neutral. But the king being a strong sympathizer of the Catholic League and the Habsburgs, decided to help the emperor. Though, he didn't want to send forces directly, he allowed Drugeth to hire mercenaries in Poland. Drugeth hired around 8,000 Lisowczycy led by Rogawski, who joined his own 3,000 men. The joined army included around 11,000 soldiers, but this number is disputed.