This map shows the development of Hungary. As part of the Austro-Hungarian empire, Hungary was one of the Central Powers in WWI. In the aftermath of WWI, Hungary was invaded by Allied forces that, in 1919, entered Budapest. With the Treaty of Trianon in 1920, the borders of Hungary were redefined to be as we know them now. This period has resulted in many occupation issues. During WWII, Hungary sided with Germany and was rewarded with a – temporary – extension of its territory.