The Yugoslav Monarchy was established in 1918 after World War I, uniting several South Slavic nations into a single kingdom. It was initially known as the Kingdom of Serbs, Croats, and Slovenes and later renamed the Kingdom of Yugoslavia in 1929. The monarchy was led by the House of Karađorđević, with King Alexander I as its first monarch. The monarchy faced numerous challenges, including ethnic tensions and political instability. In 1941, during World War II, it was invaded by Axis powers, leading to the establishment of a puppet regime. The monarchy was ultimately abolished in 1945, giving way to the socialist Federal People's Republic of Yugoslavia.