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.
Romanian anti-communist resistance movement
The rebels had links with the CIA, which conducted parachute missions in Romania in the early post-war years. At the beginning of 1949, the CIA through its OPC began to recruit displaced Romanians from Germany, Austria, and Yugoslavia. Gordon Mason, the CIA station chief in Bucharest from 1949–51, said that the smuggling of weapons, ammunition, radio transmitters, and medicine were organized. Agents smuggled into Romania by the CIA were to help organize the sabotage of factories and transport networks. In particular, a two-man team was parachuted into Romania by the CIA on 2 October 1952 near Târgu Cărbunești in Oltenia. Three American-trained agents were sent in June 1953 to the Apuseni Mountains, who were later captured, but not executed, as the Romanian authorities intended to use them as double agents. In the Oradea-Satu Mare region, three airdropped agents were killed, one of them in a firefight and two others later executed.