Subdivisions of the Kingdom of Yugoslavia

The subdivisions of the Kingdom of Yugoslavia (initially known as the Kingdom of Serbs, Croats, and Slovenes) existed successively in three different forms. From 1918 to 1922, the kingdom maintained the pre-World War I subdivisions of Yugoslavia's predecessor states. In 1922, the state was divided into 33 oblasts or provinces and, in 1929, a new system of nine banates (in Serbian and Croatian, the word for "banate" is banovina) was implemented.

From 1918 to 1922, Kingdom of Serbs, Croats, and Slovenes continued to be subdivided into the pre-World War I divisions of Austria-Hungary and the formerly independent Balkan states of Serbia and Montenegro.

The Vidovdan Constitution of 1921 established the Kingdom of Serbs, Croats, and Slovenes as a unitary state and, in 1922, 33 new administrative oblasts (counties) ruled from the center were instituted. These bore no relation to the earlier divisions.

From 1929, the Kingdom was subdivided into nine new provinces or banates called banovinas. Their borders were intentionally drawn so that they would not correspond either to boundaries between ethnic groups, or to pre-World War I imperial borders. They were named after various geographic features, mostly rivers. Slight changes to their borders were made in 1931 with the new Yugoslav Constitution. The banates (banovinas) were as follows:

The City of Belgrade, together with Zemun and Pančevo was also an administrative unit independent of the banates (banovinas).

...
Wikipedia