On 29 September the Austrians attacked Frederick's camp in Bohemia, resulting in a Prussian victory at the Battle of Soor, despite the Austrian surprise and superior numbers. Soon low supplies forced the Prussians to withdraw into Upper Silesia for the winter. In November Austria and Saxony prepared a surprise double invasion of Brandenburg, hoping to seize Berlin and end the war outright. On 23 November Frederick surprised the Austrian invaders in the Battle of Hennersdorf, confusing and scattering the larger Austrian force. Meanwhile, another Prussian army under LeopoldI of Anhalt-Dessau advanced into western Saxony, attacking and destroying the main Saxon army in the Battle of Kesselsdorf on 15 December, after which the Prussians occupied Dresden.