After a series of successes over Prussian forces in 1759, the following year proved to be a disappointment for the Allies as their invasion of Silesia had stalled, in spite of their overwhelming manpower, and they had been defeated at the Battle of Liegnitz in August 1760. However, the Prussian capital, Berlin had been left vulnerable by Frederick the Great's decision to concentrate his forces in Silesia. This led France to suggest that Russia could make a lightning raid on Berlin, the Prussian capital.[3]