The Siege of Pirna ( or Investment of Pirna ) took place Process_start in 1756 as part of the Prussian invasion Attack of Saxony during the Third Silesian War ( part of the Seven Years ' War ) .

The Siege of Pirna ( or Investment of Pirna ) took place Process_start in 1756 as part of the Prussian invasion Attack of Saxony during the Third Silesian War ( part of the Seven Years ' War ) .

Following the occupation of the capital Dresden by Frederick the Great on 9 September the Saxon army had withdrawn Escaping south and taken up position Temporary_stay at the fortress of Pirna under Frederick von Rutowski .

Following the Battle Hostile_encounter of Lobositz the Austrians withdrew Escaping , and tried to approach Pirna by a different route but they failed to make contact with the defenders .