Rákóczi returned to Sárospatak to meet with Bethlen who arrived at the head of the Transylvanian army on 17 September. They went to Kassa where Bethlen held an assembly with the deputies of the noblemen and towns of Upper Hungary. The deputies elected Rákóczi the commander of Upper Hungary on 21 September. He established his seat in Kassa. Drugeth hired irregular troops (primarily Cossacks) in Poland and broke into Zemplén County on 21 November. Rákóczi tried to stop their invasion, but he was defeated in the Battle of Humenné on 23 November. Bethlen soon lifted the siege of Vienna and hurried back to Hungary. He blamed Rákóczi for the defeat, describing him as a young and inexperienced commander in a letter to the burghers of Kassa.