Trying to simultaneously besiege Prague and face Daun, the Prussians were compelled to divide their forces. Frederick led 5,000 troops from the siege to reinforce a 19,000-man army under Bevern at nearby Kolín and assess the situation. Without sufficient force to resist Daun's advance, Frederick decided to withdraw more men from the siege and preemptively attack the Austrian position. The resulting Battle of Kolín on 18 June ended in a decisive Austrian victory; the Prussian position was ruined, and the invaders were forced to lift the siege and withdraw from Bohemia altogether, pursued by Daun's army, which was enlarged by the Prague garrison. The failure to take Bohemia meant the ruin of Frederick's strategy, leaving no prospect of a march on Vienna.