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.
Amicii URSS
During the early stages of World War II, when government in Romania was taken over by the Iron Guard fascist and pro-Nazi Germany movement ("see National Legionary State"), PCR leaders Teohari Georgescu and Lucrețiu Pătrășcanu worked together to reactivate the society, profiting from friendly relations between the new authorities and the Soviet Union; their attempt came to an abrupt end in 1941, when Ion Antonescu's triumph against the Guard provoked a collateral move against communist activists ("see Legionnaires' Rebellion and Bucharest Pogrom").