The major war in continental Europe that the British had hoped to avoid exploded in August 1756 when Frederick the Great attacked and overran the Austrian ally Saxony. Having occupied it he then launched a similarly bold invasion of Bohemia. In both cases the Prussians caught their Austrian enemies by surprise, and had used this advantage to full effect, capturing major objectives before Austrian troops had been fully mobilised. Having besieged Prague, an Austrian counter-attack and a defeat at the Battle of Kolín forced the Prussians back.