In September 1918, the Entente powers started their advance at the [[Salonica front]], [[Liberation of Serbia, Albania and Montenegro (1918)|reclaiming the territory of the occupied Serbia]]. As a part of the offensive, a task force known as the Adriatic Troops ({{lang|sr|Jadranske Trupe}}) was diverted into Montenegro ahead of supporters of Nikola or Italian forces,{{sfn|Pavlović|2008|pp=147–149}} perceived as a threat by Serbia due to Italy's demand for the establishment of an Italian [[Condominium (international law)|condominium]] in Montenegro, excluding a Serbian presence.{{sfn|Banac|1984|p=284}} The Adriatic Troops, led by Colonel {{ill|Dragutin Milutinović (soldier)|sr|Dragutin Milutinović|lt=Dragutin Milutinović}}, were tasked by the Regent with preventing the return of Nikola by any means. Accompanied by Spasojević, a member of the Montenegrin Committee, and Svetozar Tomić, head of the Montenegrin section of the Serbian Foreign Ministry, Milutinović established the Central Executive Committee for the Unification of Serbia and Montenegro on 28 October. This committee, comprising Spasojević, Tomić, and Berane mayor Milosav Raičević, was tasked with organizing a popular assembly and establishing the rules for the election of assembly delegates.{{sfn|Pavlović|2008|pp=147–149}}

In September 1918, the Entente powers started their advance at the [[Salonica front]], [[Liberation of Serbia, Albania and Montenegro (1918)|reclaiming the territory of the occupied Serbia]]. As a part of the offensive, a task force known as the Adriatic Troops ({{lang|sr|Jadranske Trupe}}) was diverted into Montenegro ahead of supporters of Nikola or Italian forces,{{sfn|Pavlović|2008|pp=147–149}} perceived as a threat by Serbia due to Italy's demand for the establishment of an Italian [[Condominium (international law)|condominium]] in Montenegro, excluding a Serbian presence.{{sfn|Banac|1984|p=284}} The Adriatic Troops, led by Colonel {{ill|Dragutin Milutinović (soldier)|sr|Dragutin Milutinović|lt=Dragutin Milutinović}}, were tasked by the Regent with preventing the return of Nikola by any means. Accompanied by Spasojević, a member of the Montenegrin Committee, and Svetozar Tomić, head of the Montenegrin section of the Serbian Foreign Ministry, Milutinović established the Central Executive Committee for the Unification of Serbia and Montenegro on 28 October. This committee, comprising Spasojević, Tomić, and Berane mayor Milosav Raičević, was tasked with organizing a popular assembly and establishing the rules for the election of assembly delegates.{{sfn|Pavlović|2008|pp=147–149}}

The rules, adopted on 7 November, stipulated that elected delegates would convene in [[Podgorica]], {{sfn|Pavlović|2008|pp=186–187}} chosen as the venue because the capital, Cetinje was a stronghold of Nikola's supporters beyond control of the assembly organisers.{{sfn|Ramet|2006|p=38}} The proponents of speedy unification with Serbia and supporters of Nikola known as the [[Whites (Montenegro)|Whites]] and [[Greens (Montenegro)|Greens]] respectively (after the colour of papers the candidate lists were printed on argued over legality and legitimacy of the election. The Whites objected because the election rules were not formulated by any Montenegrin legislative body and because they contravened the existing laws. The whites thought the election illegitimate due to lack of oversight of the voting and absence of a minimum [[voter turnout]] requirement. The Greens saw the process as a form of [[plebiscite]] that legitimised the new assembly.{{sfn|Pavlović|2008|pp=149–151}} In total, 165 delegates were to be elected.{{sfn|Bojović|1989|p=291}} The election, held on 19 November, resulted in a significant assembly majority for the Whites.{{sfn|Banac|1984|p=285}} There were allegations that the Royal Serbian Army obstructed the Greens from returning from abroad and interfering with the electoral process.{{sfn|Pavlović|2008|pp=149–151}} French authorities prevented Nikola from returning to Montenegro from his exile in [[Neuilly-sur-Seine]].{{sfn|Banac|1984|p=284}} The [[Podgorica Assembly]] convened on 24 November. Two days later it voted to remove Nikola from the Montenegrin throne and to decide that Montenegro and Serbia would be united under Serbia's ruling Karađorđević dynasty, joining the common state of the "three-named people" (Serbs, Croats, and Slovenes). Further decisions were to elect an executive committee to coordinate the unification work, and to send notices of the resolution to Nikola, the Serbian government, as well as allied and neutral countries.{{sfn|Pavlović|2008|pp=157–163}} The decision was unanimously adopted, with three delegates absent from the vote.{{sfn|Banac|1984|p=285}}

The rules, adopted on 7 November, stipulated that elected delegates would convene in [[Podgorica]],{{sfn|Pavlović|2008|pp=186–187}} chosen as the venue because the capital, Cetinje was a stronghold of Nikola's supporters beyond control of the assembly organisers.{{sfn|Ramet|2006|p=38}} The proponents of speedy unification with Serbia and supporters of Nikola known as the [[Whites (Montenegro)|Whites]] and [[Greens (Montenegro)|Greens]] respectively (after the colour of papers the candidate lists were printed on argued over legality and legitimacy of the election. The Whites objected because the election rules were not formulated by any Montenegrin legislative body and because they contravened the existing laws. The whites thought the election illegitimate due to lack of oversight of the voting and absence of a minimum [[voter turnout]] requirement. The Greens saw the process as a form of [[plebiscite]] that legitimised the new assembly.{{sfn|Pavlović|2008|pp=149–151}} In total, 165 delegates were to be elected.{{sfn|Bojović|1989|p=291}} The election, held on 19 November, resulted in a significant assembly majority for the Whites.{{sfn|Banac|1984|p=285}} There were allegations that the Royal Serbian Army obstructed the Greens from returning from abroad and interfering with the electoral process.{{sfn|Pavlović|2008|pp=149–151}} French authorities prevented Nikola from returning to Montenegro from his exile in [[Neuilly-sur-Seine]].{{sfn|Banac|1984|p=284}} The [[Podgorica Assembly]] convened on 24 November. Two days later it voted to remove Nikola from the Montenegrin throne and to decide that Montenegro and Serbia would be united under Serbia's ruling Karađorđević dynasty, joining the common state of the "three-named people" (Serbs, Croats, and Slovenes). Further decisions were to elect an executive committee to coordinate the unification work, and to send notices of the resolution to Nikola, the Serbian government, as well as allied and neutral countries.{{sfn|Pavlović|2008|pp=157–163}} The decision was unanimously adopted, with three delegates absent from the vote.{{sfn|Banac|1984|p=285}}

With the acquiescence of the National Council achieved, the Kingdom of Serbs, Croats and Slovenes was declared on 1 December 1918 in Belgrade.{{sfn|Cukić|Kastratović-Ristić|Vasiljević|2019|p=22-26}}

With the acquiescence of the National Council achieved, the Kingdom of Serbs, Croats and Slovenes was declared on 1 December 1918 in Belgrade.{{sfn|Cukić|Kastratović-Ristić|Vasiljević|2019|p=22-26}}