Query: Where did the Austrians retreat in May of 1757?
Context: In early 1757, Frederick II again took the initiative by marching into the Kingdom of Bohemia, hoping to inflict a decisive defeat on Austrian forces. After winning the bloody Battle of Prague on 6 May 1757, in which both forces suffered major casualties, the Prussians forced the Austrians back into the fortifications of Prague. The Prussian army then laid siege to the city.