Hungary–Romania relations
During World War II, Hungary and Romania became allies and participated in the war against the Soviet Union. But after the coup on 23 August 1944 Romania switched sides and fought against Hungary. Consequently, Soviet and Romanian troops invaded Hungary, occupied Northern Transylvania by October 1944 and re-established the Romanian administration in the region in March 1945. The 1947 Treaty of Paris reaffirmed the borders between Romania and Hungary as originally defined in Treaty of Trianon 27 years earlier, thus confirming the return of Northern Transylvania to Romania.
Romania in World War II
The Romanian Army ended the war fighting against the Wehrmacht alongside the Red Army in Transylvania, Hungary, Yugoslavia, Austria and Czechoslovakia, from August 1944 until the end of the war in Europe. In May 1945, the First and Fourth armies took part in the Prague Offensive. The Romanian Army incurred heavy casualties fighting Nazi Germany. Of some 538,000 Romanian soldiers who fought against the Axis in 1944–45, some 167,000 were killed, wounded or went missing.