On 29 October 1918 the Croatian Parliament (''Sabor'') declared independence and decided to join the newly formed State of Slovenes, Croats, and Serbs, which in turn entered into union with the Kingdom of Serbia on 4 December 1918 to form the Kingdom of Serbs, Croats, and Slovenes. The Croatian Parliament never ratified a decision to unite with Serbia and Montenegro. The 1921 constitution defining the country as a unitary state and abolition of Croatian Parliament and historical administrative divisions effectively ended Croatian autonomy.