In 1531 Peter IV Rareş invaded Poland in order to reoccupy the Pocuţia region (in modern Ukraine), but his army was defeated. Now he concluded a secret treaty with Ferdinand I of Hungary, but soon had to seek refugee in Transylvania when Suleiman I led an army against him. This was the first occasion when a prince, Stephen V Lăcustă (1538–1540) was appointed by the sultan. At the same time, the sultan occupied Brăila and Tighina (now in Moldova), and the Budjak region (now in Ukraine). Peter IV Rareş recovered his throne in exchange for a large sum of money in 1541. His death was followed by a period characterized by fights between pretenders to the throne and among the "boyar" parties.