 After World War II, Croatia — including Slavonia — became a single-party Socialist federal unit of the Socialist Federal Republic of Yugoslavia, ruled by the Communists, but enjoying a degree of autonomy within the federation. The autonomy effectively increased after the 1974 Yugoslav Constitution, basically fulfilling a goal of the Croatian Spring movement, and providing a legal basis for independence of the federative constituents. In 1947, when all borders of the former Yugoslav constituent republics had been defined by demarcation commissions, pursuant to decisions of the AVNOJ of 1943 and 1945, the federal organization of Yugoslav Baranya was defined as Croatian territory allowing its integration with Slavonia. The commissions also set up the present-day 317.6-kilometre (197.3 mi) border between Serbia and Croatia in Syrmia, and along the Danube River between Ilok and mouth of the Drava and further north to the Hungarian border, the section south of confluence of the Drava matching the border between the Kingdom of Croatia-Slavonia and the Bács-Bodrog County that existed until 1918 and the end of World War I.
