Kingdom of Serbs, Croats and Slovenes, 1918
Kingdom of Yugoslavia, 1929
On 1 December 1918, the newly formed State of Slovenes, Croats and Serbs joined the Kingdom of Serbia and the Kingdom of Montenegro to form the Kingdom of Serbs, Croats and Slovenes, with Peter I, the king of Serbia, becoming the first monarch of the new kingdom. The flag was a blue-white-red tricolour - pan Slavic colours that also were those of the other Slav peoples, but in a particular order. In 1929 King Alexander I officially changed the country’s name to “Yugoslavia”, a name that had already unofficially been used and meant “country of the South Slavs”.