 Advocacy in favour of Yugoslavism as a means to achieve the unification of Croatian lands in opposition to their division under Austria-Hungary began with Strossmayer advocating this as being achievable within a federalized Yugoslav monarchy.After the foundation of Yugoslavia in 1918, a highly centralized state was established in the St. Vitus Day Constitution of 1921 in accordance with Serbian nationalist desires to ensure the unity of the Serbs, this caused resentment amongst Croats and other peoples in Yugoslavia.Dalmatian Croat and the principal World War I-era Yugoslavist leader Ante Trumbić denounced the St. Vitus Day Constitution for establishing a Serb hegemony in Yugoslavia contrary to the interests of Croats and other peoples in Yugoslavia.