Four more kingdoms formed in what had been eastern Iran. However, Khwarezm was soon conquered by Turkish settlers, while Khorasan, Baktristan and Sakastan were by 960 reunited into a strong empire, ruled first by the Samanid Dynasty and then by the Shansabanids. The east was conquered by the Mongols in the 1220s, who attempted to venture further west but abandoned such ambitions after the 1255 Battle of Arbela.