Editing Yugoslav Committee (section)

===Niš Declaration===
{{main|Niš Declaration}}
[[File:Serbia1913.png|thumb|right|upright=0.7|Map of the [[Kingdom of Serbia]] before the [[World War I]]]]

The Serbian leadership considered World War I to be an opportunity for territorial expansion beyond the Serb-inhabited areas of the [[Balkans]]. A committee that was tasked with determining the country's war aims produced a program to establish a single South-Slavic state through the addition of Croatia-Slavonia, the [[Slovene Lands]], [[Serbian Vojvodina|Vojvodina]], [[Condominium of Bosnia and Herzegovina|Bosnia and Herzegovina]], and Dalmatia.{{sfn|Pavlowitch|2003a|p=29}} Pašić thought the process should be implemented through the addition of new territories to Serbia.{{sfn|Banac|1984|pp=118–119}} On 7 December, Serbia announced its war aims in the [[Niš Declaration]].{{sfn|Lampe|2000|pp=102–103}} The declaration called on South Slavs to struggle to liberate and unify "unliberated brothers",{{sfn|Ramet|2006|p=40}} "three tribes of one people"&nbsp;– referring to  Serbs, Croats, and Slovenes.{{sfn|Lampe|2000|pp=102–103}} This formulation was adopted instead of an explicit goal of territorial expansion as a way to attract support from South Slavs living in Austria-Hungary. The Serbian government wanted to appeal to fellow South Slavs because it feared little material support would be delivered from its Entente Powers allies as it became clear the war would not be short.{{sfn|Lampe|2000|pp=102–103}} Serbia assumed a central role in the state-building of the future South Slavic polity, with support from the major Entente Powers.{{sfn|Pavlović|2008|p=70}}

Supilo initially assumed the Niš Declaration meant Serbia was fully supportive of his ideas on the method of unification. He was convinced otherwise by Russian foreign minister [[Sergey Sazonov]], who informed Supilo that Russia only supported the creation of Greater Serbia.{{sfn|Boban|2019|p=19}} As a result, Supilo and Trumbić did not trust Pašić, and considered him a proponent of Serbian hegemony.{{sfn|Ramet|2006|pp=41–42}} Despite the mistrust, Supilo and Trumbić wanted to work with Pašić to further the aim of South-Slavic unification. Pašić offered to work with them towards the establishment of a Serbo-Croat state in which Croats would be given some concessions, an offer they declined.{{sfn|Banac|1984|pp=118–119}} Trumbić was convinced the Serbian leadership thought of unification as a means to conquer neighbouring territories for Serbian gain.{{sfn|Banac|1984|p=119}}

Trumbić and Supilo found another reason to distrust Pašić when Pašić dispatched envoys to address Sazonov's opposition to the addition of Roman Catholic South Slavs to the proposed South Slavic union. The envoys wrote a memorandum claiming Croats only inhabit the north of Central Croatia, and that the regions of Slavonia, [[Krbava]], [[Lika]], [[Bačka]], and [[Banat]] should be added to Serbia, as well as the previously claimed Dalmatia, and Bosnia and Herzegovina.{{sfn|Boban|2019|pp=19–20}} Trumbić and Supilo became convinced that because of the Government of Serbia's expansionist policy, the proposed unification would be perceived within Croatian-inhabited areas of Austria-Hungary as a Serbian conquest rather than as a liberation. They decided to proceed with caution, gather political support abroad, and to refrain from the establishment of a Yugoslav Committee until Italy's entry into the war became certain.{{sfn|Boban|2019|p=17}}