From 1918 to 1941, Serbia did not existed as a political entity, since SCS Kingdom (Kingdom of Yugoslavia) was a centralist country divided into administrative provinces that were not created in accordance with ethnic or historical criteria. However, the country was ruled by Serb king and dominated by Serb political elite. This triggered the unsatisfactoriness among the Croats, whose politicians demanded federalization of the country. The Serb-Croat political compromise was achieved in 1939 when new province known as the Banovina of Croatia was created. Some Serb intellectuals also demanded that the rest of the Yugoslav provinces (excluding the Drava Banovina) are joined into the new Banovina of Serbia, but this political project was never realized.
In 1941, after the Axis invasion and occupation of Yugoslavia, German occupational authorities created an occupied territory named Serbia and installed Serbian puppet government there. Occupied Serbia included much of the territory of present-day Republic of Serbia, excluding some areas that were occupied and annexed by Independent State of Croatia, Hungary, Bulgaria, and Italy. The Banat region, which was a part of occupied Serbia, had a special autonomous status and was governed by its ethnic German minority. Besides the armed forces of the Serbian pro-Axis puppet regime, two anti-Axis resistance movements operated in the territory of Serbia: the royalist Chetniks and the communist Partisans. Besides the anti-Axis orientation, the two resistance movements also turned one against another, which resulted in a general armed civil war in Serbia. Temporarily, in autumn of 1941, the communist resistance movement created a short lived Republic of Užice in south-western Serbia, but this entity was soon destroyed by the joint efforts of Axis troops and pro-Axis Serbian armed forces.
In 1944, the SovietRed Army and Yugoslav Partisans expelled Axis troops from Serbia and the area was included into the restored Yugoslavia. Unlike the pre-war Yugoslavia, which had a centralist system of government, the post-war Yugoslavia was established as a federation of six equal republics. One of the republics was Serbia, which had two autonomous provinces: Vojvodina and Kosovo. According to the 1974 Yugoslav constitution, the autonomous provinces of Serbia gained extensive political rights and were in some areas presented in federal government separately from Serbia, although, they were still de jure subordinated to Serbia.