Siege of Copenhagen (1658)

On August 11, 1658 Karl X and his forces reached Valby hill (current day Frederiksberg) from where they could overlook the Danish capital. His arrival was expected and Danish King Frederick III had already ordered every building outside the city walls burnt, even though it had housed a third of the population of the city. That same day the city gates were closed and would not open again for another 22 months. A Swedish fleet of 28 ships blocked the harbor, preventing resupply by sea. The siege had begun.

When the Swedish king arrived to find half the city in flames and the Danes willing to put up a fight he had a difficult decision to make, whether to press forward immediately or whether to lay siege on the city and try to starve it out. His advisers were divided on the issue, and the king ultimately decided on the latter route. The wisdom of this decision has been questioned, since the Danish defenses were in poor shape initially. However, the population of Copenhagen rallied behind Frederick III, and the walls, moats and other defensive structures of the city were quickly improved. A large number of cannons were brought into the city from ships anchored in the harbor and placed along likely attack routes. The city also had plenty of defensive materiel: 50 t of lead, 4,000 muskets, and a staggering 810 km of slow match.

The Swedish siege force consisted of 11 brigades and 16 squadrons comprising 4,000 infantry, 2,000 cavalry and 50 cannons. The Swedes took the outer defensive perimeter, built in 1625 by Christian IV, which had fallen into disrepair. It was hastily repaired and artillery was brought to bear on the city. The Danes would not let the Swedish attack go uncontested, and made several counter-attacks. On August 23, 1658, almost 3,000 students, sailors and soldiers staged a surprise sortie through a hidden passage in the wall, destroying fortifications under construction and capturing three cannons.

Over 200 heated shot a day were hurled into the city, and several large howitzers were brought to bombard the Danish capital, including the 300-pounder "Eric Hansson", earlier used in the siege of Kraków. But the citizens of Copenhagen proved to be resilient and endured the constant barrage.