of Nyboder were changed into ordinary residences. In 1868 it was decided to remove the ramparts and from 1872 the old glacises were converted into residential areas. By the construction of Frihavn harbour in 1894 another neighbourhood was founded stretching towards Hellerup. In 1900–01, the large developments of Brønshøj and Valby followed. The Second War of Schleswig in 1864 (where Denmark lost a third of its area) was the primary reason the old ramparts were replaced by the Fortification of Copenhagen. 20th century During World War II Copenhagen was occupied by German troops along with the rest of the country from April 9, 1940, until May 4, 1945. In August 1943, when the government's collaboration with the occupation forces collapsed, several ships were sunk in Copenhagen Harbour by the Royal Danish Navy to prevent them being used by the Germans. Operation Carthage (the bombardment of the Shellhouse, the headquarters of the Gestapo) took place on March 21, 1945, by British de Havilland Mosquito bombers. During this attack the French School at Frederiksberg was also mistakenly bombed resulting in the death of many children. On 8 May 1945 Copenhagen was officially liberated by British troops led by Field Marshal Bernard Montgomery who supervised the surrender of 250,000 German armed forces across Denmark of which near on 30,000 were situated around the capital. The city has grown greatly since the war. In the 1970s, the so-called five-finger-plan provided commuter train links to the surrounding towns and suburbs. Conditions in the central city deteriorated rapidly in the 1980s and 1990s. Financially the city verged on bankruptcy. Negative factors included de-industrialization, flight to the suburbs, high unemployment, escalating welfare, dilapidated housing, and ethnic strong segregation. The city recovered rapidly by 2010, thanks to its service- and knowledge-based economy. In 1992 construction on the Copenhagen Metro and in 1993 development of a new city area, the Ørestad, began on the island of Amager. The metro underground train system opened for traffic in 2002. Since the summer of 2000, the cities of Copenhagen and Malmö have been connected by a toll bridge, the Øresund Bridge, for both rail and road traffic. It was inaugurated in July 2000 by Carl XVI Gustaf of Sweden and Margrethe II of Denmark. As a result, Copenhagen has become the centre of a larger metropolitan area spanning both nations. The construction of the bridge has brought about significant changes in the