With the new powers afforded to Batu by Möngke, he now had direct control over the Rus' princes. However the Grand Prince Andrey II refused to submit to Batu. Batu sent a punitive expedition under Nevruy, who defeated Andrey and forced him to flee to Novgorod, then Pskov, and finally to Sweden. The Mongols overran Vladimir and harshly punished the principality. The Livonian Knights stopped their advance to Novgorod and Pskov. Thanks to his friendship with Sartaq Khan, Batu's son, who was a Christian, Alexander was installed as the Grand Prince of Vladimir (i.e., the supreme Russian ruler) by Batu in 1252.