When World War I broke out in 1914, Croats fought in Habsburg armies on all fronts, including against Serbia. When the Habsburg Empire collapsed in 1918 however most Croatian leaders were eager to join Serbia in the creation of a Yugoslav state (initially called the Kingdom of Serbs, Croats and Slovenes, it changed its name to Yugoslavia in 1929).

The main reason for this enthusiasm was fear of Italian designs on the Adriatic coast and the need for a unified response to any future international threats. The new country’s King would be chosen from Serbia’s royal house, the Karađorđević dynasty.

A centralized state

Croatian leaders initially assumed that the new state would accord full autonomy to its various peoples, only to be disappointed with the passing of the rigid, centralist Vidovdan constitution in 1921. Attempts to reform the new country and increase Croatian autonomy became the main theme of Croatian politics for the next two decades.

Assassinations & uncertainty