An Austrian army led by the Count von Daun made a sudden march to the north, threatening Frederick's lines of supply, and he was forced to break off the siege and march to attack them. Frederick was defeated at the Battle of Kolín and his force was now too weak to contemplate continuing the siege of Prague, and he was forced to withdraw from Bohemia entirely. It marked a high-water mark for the Prussians, as they would never hold so advantageous a position again and most of the remainder of the war would be fought on their own territory. In spite of this the Prussians attempted another invasion of Austrian territory the following year which culminated in a failed attempt to take Olomouc.