The death of Christian IV in 1648 meant the end of the 30-year war, but his successor Frederick III commenced war against Sweden. Copenhagen was occupied and Swedes sought to invade Møn by walking across the ice from Zealand. This was prevented by the islanders, who maintained a three-mile long opening in the ice to stop the invasion force. However, in May 1659, 3,000 Swedes invaded from the island of Bogø against a force of 500 defenders. Stege was occupied, the town hall and 300 farms destroyed, the island looted and the harvest lost. At the end of the war, in 1660, the island's population was reduced to 670.