after the assassination in sarajevo of archduke franz ferdinand and the invasion of serbia by austria-hungary, trumbić became the prominent yugoslav nationalist leader during world war i, and led the yugoslav committee that lobbied the allies to support the creation of an independent yugoslavia. trumbić negotiated with serbian prime minister nikola pašić to have the kingdom of serbia support the creation of a yugoslav state, which was delivered at the corfu declaration on 20 july 1917 that advocated the creation of a united state of serbs, croats and slovenes that would be led by the serbian house of karađorđević.