After the World War II in Yugoslavia, the country was ruled by the Communist Party of Yugoslavia (KPJ) which adopted a formal commitment to federalism in a highly centralised state, promoting social Yugoslavism and diversely interpreted notion of "brotherhood and unity". The 1948 Tito–Stalin split pushed the KPJ to gradual decentralisation until mid-1950s when a Yugoslavist campaign was launched to reverse the course leading to a debate on levels of (de)centralisation. Centralist forces were defeated by mid-1960s. Significant decentralisation occurred during and in the aftermath of the Croatian Spring. Yugoslavism was cited by Slovenian intellectuals in 1987 as the main threat to Slovenian identity. The issues raised by them contributed to motivation for a 1990 proposal to restructure Yugoslavia as a confederation and for subsequent Slovenian and Croatian declarations of independence marking the breakup of Yugoslavia.