The Yugoslav Kingdom, officially known as the Kingdom of Serbs, Croats, and Slovenes, was established in 1918 after World War I. It united several South Slavic nations under a single monarchy, with King Alexander I as its first ruler. The kingdom aimed to promote unity among diverse ethnic groups, but faced challenges due to regional differences and political tensions. In 1929, the kingdom was renamed the Kingdom of Yugoslavia and underwent significant political changes, including the introduction of a royal dictatorship. The kingdom struggled with internal conflicts and economic difficulties, ultimately leading to its disintegration during World War II.