Hungary was conquered by the Habsburgs in the 17th century, becoming an equal partner in the Austro-Hungarian empire in 1867. Following the collapse of the empire in 1918, Hungary became an independent kingdom. After participation in the Second World War on the Axis side, Hungary was occupied by the USSR, and became a communist state. A liberal reform movement was crushed by Soviet troops in 1956, but the communist system was abandoned in 1989, and the first multiparty elections were held in 1990. Hungary joined NATO in 1999 and the EU in 2004.