While early postwar musical modernist explorations seemed progressive during the 1950s, Yugoslav composers faced European and American avant-garde trends at the inaugural Music Biennale Zagreb in 1961. Founded by Croatian composer Milko Kelemen, who refused to conform to the demands of socialist realism, the Zagreb Biennale was the most significant cultural event in Yugoslavia in the early 1960s and continued to play a pivotal role in the country’s cultural diplomacy over the next three decades. Taking advantage of the Cold War political divisions, Yugoslavia’s unique position as a “liberal” communist state that did not belong to either bloc, and an economic model that adopted elements of socialism and capitalism, Kelemen devised a plan that reads like a Cold War spy novel. Pitting the Soviets against the Americans and Western Europeans with fabricated stories, Kelemen managed to secure the participation of the most recognizable figures in contemporary music in the US and Europe. Consequently, his festival became one of the most relevant international festivals of contemporary music and a forum for Yugoslavia’s engagement with Western avant-gardism.