On April 23, 1639, the town was invaded by Swedish troops under the commander in chief of the Swedish army, Johan Banér. During the five-month long siege of the fortress, which was in the end futile, the town was greatly devastated. About 600 people were murdered ("Pirnaisches Elend", lit. "Misery of Pirna"). In around 1670, based upon recent military developments, the Sonnenstein fortress was built. Only the powerful stonework still exists today. In 1707, Pirna had debts that related to the Great Northern War of more than 100,000 Thalers.