Abandoned agreement on the creation of Yugoslavia
The Geneva Declaration, Geneva Agreement, or Geneva Pact was a statement of political agreement on the provisional political system in the future union of the South Slavs living in the territories of the former Austro-Hungarian Empire and Kingdom of Serbia. It was agreed by Serbian Prime Minister Nikola Pašić on behalf of Serbia, representatives of Serbian parliamentary opposition, representatives of the National Council of the State of Slovenes, Croats and Serbs which recently seceded from Austria-Hungary, and representatives of the Yugoslav Committee. The talks held in Geneva, Switzerland on 6–9 November 1918 built upon and were intended to supersede the 1917 Corfu Declaration agreed by Pašić and Yugoslav Committee president Ante Trumbić. The basis for the talks was provided by the Greek Prime Minister Eleftherios Venizelos on behalf of the Supreme War Council of the Triple Entente. The talks were necessary in the process of creation of Yugoslavia as a means to demonstrate to the Entente powers that various governments and interests groups could cooperate on the project to establish a viable state.
Trumbić and Anton Korošec leading delegations of the Yugoslav Committee and the National Council of Slovenes, Croats and Serbs respectively generally conducted the negotiations from a common platform. The Serbian opposition sided with the Yugoslav Committee aiming to undermine Pašić's hold on power. Trumbić's proposal to establish a confederal system of government was adopted. It envisaged a common government having foreign affairs, defence, common finances, communications and transport, as well as several other departments. The proposal also specified retaining the Serbian government and the National Council as the executive in the State of Slovenes, Croats and Serbs to manage affairs relevant for the two states separately. Pašić also agreed to recognise the National Council as a legitimate government and to ask the Entente to do the same. Pašić accepted the Geneva Declaration only after President of France Raymond Poincaré personally intervened telling him to agree with the Yugoslav Committee.
The Serbian government first accepted the declaration, and only days later reversed the course when Pašić suggested in a message to his finance minister Stojan Protić that the Prince Regent Alexander might use his prerogative to reshuffle the government. The government rejected the Geneva Declaration and resigned—only to be replaced two days later by a coalition government led by Pašić and including the former opposition in its ranks. In the State of Slovenes, Croats and Serbs, the leader of the largest political party, the Croat-Serb Coalition Svetozar Pribićević, rejected the Geneva Declaration as well. Faced with internal unrest caused by the Green Cadres, peasant revolts, and mutinies in the military, as well as the approaching Italian Army enforcing Italian territorial claims under the Treaty of London following the Armistice of Villa Giusti, the National Council dispatched a delegation to seek urgent unification from Prince Regent Alexander—leading to establishment of the Kingdom of Serbs, Croats and Slovenes on 1 December 1918.
Background.
Corfu Declaration.
During World War I, the government of Serbia, led by Prime Minister Nikola Pašić, met with the ad-hoc interest group Yugoslav Committee. The committee, partially funded by Serbia, was chaired by Ante Trumbić and claimed to represent the South Slavs living in Austria-Hungary. The conference was convened in 1917 on the Greek island of Corfu to discuss the system of government in a future union of Serbia and South Slavic-populated Habsburg lands. 
The meeting was meant to recapture initiative for Yugoslavist ideas on the unification of South Slavs, and to preserve chances for achieving the expansionist Serbian war aims set out in the Niš Declaration. Both were thought to be in jeopardy following a trialist reform proposed in the May Declaration of the Yugoslav Club of South Slavic representatives in the Austrian Imperial Council, led by Anton Korošec, while Serbia's allies in the Triple Entente were still supporting the preservation of Austria-Hungary. Deprived of Russian backing since the February Revolution, Pašić felt compelled to negotiate with the Yugoslav Committee.
Yugoslav Committee members learned that the Entente, under the 1915 Treaty of London, had promised Italy parts of Austro-Hungarian territory inhabited by South Slavs to entice Italy to join the Entente. Most of the committee members saw that as a threat that could only be checked with help from Serbia, prompting them to accept Pašić's invitation to Corfu. Frano Supilo, the co-founder of the ruling Croat-Serb Coalition (HSK) in Croatia-Slavonia and the most prominent member of the Yugoslav Committee and advocate of a South Slavic federation, resigned his committee membership in protest. Supilo resigned because his caution against discussions without determining Serbian intentions first were ignored.
The Corfu conference revealed a conflict between Pašić and Trumbić, as the former advocated a centralised state while the latter wanted a federal system of government, fearing a hegemony of the Serbs as the most populous ethnic group in the proposed state. In response to Trumbić's demands, Pašić said that if the Croats insisted on a federation, the Serbian government would abandon the unification project in favour of creation of a Greater Serbia. No agreement on the system of government was reached and the adopted Corfu Declaration left the matter for the future Constituent Assembly to decide by an unspecified qualified majority.
Pašić–Trumbić conflict.
It was apparent in the aftermath of the Corfu conference, relations between Pašić and Trumbić worsened and kept deteriorating throughout 1918. The two openly disagreed on several issues advocated by Trumbić including the matter of recognition of the Serbs, Croats, and Slovenes living in Austria Hungary as allied peoples, recognition of the Yugoslav Committee as the representative of those peoples and the Serbs, Croats, and Slovenes Volunteer Corps as an allied force drawn from Serbs, Croats, and Slovenes living in Austria-Hungary. Unable to achieve those goals on his own, Trumbić wanted Pašić to help persuade the Entente powers to grant Trumbić's requests. Their relations remained tense, but despite ignored pleas to Pašić, they remained in contact until the end of the war. Pašić and Trumbić met again on 30 October in Paris. Pašić rejected Trumbić once again, but this time, Trumbić asked the remainder of the Yugoslav Committee to authorise him to seek fulfilment of his earlier requests from the Entente powers directly, bypassing Pašić. The Yugoslav Committee agreed the next day.
Besides the rejection of Trumbić's demands, friction was caused by Pašić's response to the Entente regarding potential preservation of Austria-Hungary. The United Kingdom, France, and the United States pursued separate peace with Austria-Hungary detaching it from Germany until early 1918. This position was not affected by Niš or Corfu declarations. In January 1918, the Prime Minister of the United Kingdom David Lloyd George confirmed his support to survival of Austria-Hungary. The President of the United States Woodrow Wilson agreed in his Fourteen Points speech by advocating autonomy for the peoples of Austria-Hungary. In April, this prompted Pašić to direct Serbian ambassador to the United States to investigate if Serbia could receive Bosnia and Herzegovina as the minimum addition to its pre-war territory.
On 15 October, Lloyd George and Pašić met in London to discuss creation of a unified South Slavic state with or without Serbia – in the latter case potentially within reformed Austria-Hungary. On Pašić's insistence that any South Slavic state created without Serbia makes its losses meaningless, Lloyd George replied that everything depended on circumstances at the end of the war: He pointed out that if the Serbian Army occupied desired territory before an armistice Serbia could annex it. Otherwise, there would be negotiations to consider wishes of affected populations. On 12–17 October, Pašić gave several interviews to the British press. Accused of imperialism, Pašić replied that Serbia was liberating the Croats and the Slovenes who will be given the chance to choose to join Serbia or establish own states. He mentioned no possibility of establishment of a South Slavic political union of equals.
Supported by British historians Wickham Steed and Arthur Evans, Trumbić unsuccessfully asked Wilson to deploy US troops to Croatia-Slavonia to quell disorder associated with the Green Cadres and stem the tide of Bolshevism. Trumbić specifically asked not to allow Italian or Serbian troops into the territory. Relations between Pašić and Trumbić deteriorated to political and even personal animosity. By the end of 1918, Trumbić thought that Pašić should be toppled from power as an oligarch.
National Council becomes involved.
On 5–6 October, representatives of Austro-Hungarian Croat, Serb, and Slovene political parties organised the National Council of Slovenes, Croats and Serbs to work to independence. On 18 October, the body declared itself the central organ of the newly proclaimed State of Slovenes, Croats and Serbs encompassing the Slovene Lands, Croatia-Slavonia, Dalmatia, and Bosnia and Herzegovina. The National Council elected Korošec its president. It had two vice presidents. One was Svetozar Pribičević – a co-founder of the ruling HSK and the coalition's sole leader since Supilo's death in 1917. Another vice president was Ante Pavelić, the leader of the Mile Starčević faction of the Party of Rights.
On 26 October, the National Council decided to authorise the Yugoslav Committee to speak on behalf of the council. On the same day, Korošec met Austrian Minister-President Heinrich Lammasch in Vienna and proceeded with Yugoslav Club secretary Gregor Žerjav to Switzerland where they were met by Melko Čingrija, another former Yugoslav Club member, on 29 October. Korošec was tasked by the National Council to "reconnoiter the international situation and establish contact with the Yugoslav Committee". The same day, the Croatian Sabor declared the end of ties with Austria-Hungary and elected Korošec the president of the State of Slovenes, Croats and Serbs. Pavelić and Pribićević were elected vice presidents.
Upon learning of Korošec's arrival, Pašić and Trumbić both reached out to him. Trumbić wrote to Korošec on 31 October outlining his talks with Pašić and asking for recognition of the Yugoslav Committee as a body representing interests of peoples living in the newly declared state. Pašić saw Korošec as a potential alternative to Trumbić having legitimacy of being an elected representative. He prepared to travel with Serbian opposition representatives Milorad Drašković and Marko Trifković to Switzerland to meet Korošec. On 1 November, Korošec invited Trumbić and Pašić to separate talks in Geneva. Korošec could not travel to Paris because he was issued visa for the neutral Switzerland only.
November conference.
Paris talks.
Trumbić wrote to Pašić on 11 October 1918 proposing to reconvene parties to the Corfu Declaration and representatives of the Montenegrin Committee for Unification in Paris in two weeks to ensure, facilitate, and expedite unification. Even though Pašić wrote back on 25 October inviting Trumbić to visit him in Paris, Pašić ignored the 11 October proposal. On 1 November, in a report to the Prince Regent, Pašić requested a message to be forwarded to Pribičević through Serbian Army liaison officer in Zagreb, Lieutenant Colonel Dušan Simović. In the message, Pašić asked Pribičević to cooperate with him on urgent unification to defend against Italian irredentism. In response, Pribičević provided regular information on political situation to Simović.
According to Trumbić, British Foreign Secretary Arthur Balfour was willing to recognise South Slavic population of Austria-Hungary as an allied nation on that day, but the recognition was withheld on request of French Foreign Minister Stephen Pichon until the British and the French agreed on the matter. On 29 October, the Supreme War Council met in Versailles, a day after Austria-Hungary requested armistice. While the terms were discussed, the French Prime Minister Georges Clemenceau promised Italian Prime Minister Vittorio Emanuele Orlando no Balkan Slavic state would be recognised before the terms of the armistice were implemented. The Entente allies also declined to recognise the State of Slovenes, Croats and Serbs or the Serbian claim of being the central unifying force among the South Slavs like Piedmont in Italian unification. The Supreme War Council also decided not to recognise any formal role of Yugoslav Committee deeming South Slavic unification unrealistic until the parties demonstrate their ability to come to an agreement. Serbia added its opposition to recognition of any official role of the Yugoslav Committee. Armistice of Villa Giusti, ending the war for Austria-Hungary was signed on 3 November. By that time, Serbian Army and the rest of the Allied Army of the Orient reached Sava and Danube rivers in Belgrade – the prewar Austro-Hungarian border.
On 3 November, Lloyd George and Balfour informed the Serbian government and opposition, as well as Trumbić and Korošec through Greek Prime Minister Eleftherios Venizelos