The declaration of the state unity of Serbs, Croats and Slovenes was preceded by the conclusions of the National Council of Slovenes, Croats and Serbs and decisions on the unification of Vojvodina and Montenegro with Serbia. The National Assembly of Serbs, Croats, Bunjevci, Slovaks, Ruthenians and other peoples from Banat, Bačka and Baranja adopted the Decision on the Inclusion of Vojvodina in the Kingdom of Serbia on November 25, 1918. The Great National Assembly of the Serbian People in Montenegro decided in Podgorica on November 26, 1918 "that Montenegro should unite in one state with brotherly Serbia." Meanwhile, developments forced the Central Committee of the National Council of Slovenes, Croats and Serbs to adopt, after some deliberation, a decision on the unification with Serbia on November 24, 1918 and to send a delegation to Belgrade. Once the delegation and Serbian Government members had coordinated their stands on the provisional organisation of the united state before the adoption of the Constitution, Crown Prince Alexander Karadjordjević proclaimed the Kingdom of Serbs, Croats and Slovenes at Krsmanović's House on Terazije Square in Belgrade.
In the address read out by Ante Pavelić a.k.a. "the dentist" in the presence of Crown Prince Alexander, Serbian Government members and delegation from Zagreb, the conclusions were made that the National Council of Slovenes, Croats and Serbs should "declare the unification of the state of Slovenes, Croats and Serbs with Serbia and Montenegro in a single state," that King Peter I, that is Regent Alexander Karadjordjević, should rule throughout the territory of the newly created state and that the single parliamentary government and people's representative office should be created. The National Council expressed its wish that the Provisional National Office be formed in agreement between the National Council and representatives of the people of the Kingdom of Serbia, that the government's responsibility towards parliament be established, that the existing provincial administrations remain in place and remain accountable to autonomous representative offices and under state control, that the Constituent Assembly be elected on the basis of the general, equal, secret and proportional right to vote and that the final state borders correspond with ethnic borders in accordance with the principle of self-determination.
In his response to the Address, Crown Prince Alexander on behalf of King Peter I declared the "unification of Serbia with the countries of the independent state of Slovenes, Croats and Serbs into the unified Kingdom of Serbs, Croats and Slovenes," and said that he would establish a government that would be accountable to the national office and whose first and foremost task would be to determine the state borders in accordance with ethnographic principles.
Regent Alexander declared Serbia's unification with the countries belonging to the independent state of Slovenes, Croats and Serbs, rather than with the state of Slovenes, Croats and Serbs which had not been internationally recognised.
As the "constituent act" the December 1 declarations represented the basis of the state and legal organisation in the newly created Kingdom of Serbs, Croats and Slovenes from unification to the adoption of the St Vitus's Day Constitution in 1921. In this period, King or Regent Alexander, Government and provisional national office represented the top authority in the Kingdom of Serbs, Croats and Slovenes. The first government of the Kingdom of Serbs, Croats and Slovenes was created on December 20, 1918 and the Provisional National Office met on March 1, 1919.
List of Constituent Acts of Yugoslavia