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.
Invasion of Yugoslavia
While Romania did not take part in the actual invasion of Yugoslavia, it did provide artillery support for the German forces invading from its territory. Operating on orders from the 3rd Section of the Romanian General Staff, Romanian artillery opened fire against Yugoslav barges on the Danube on 6 April. Romanian and German units from the Romanian bank of the Danube repeatedly exchanged fire with Yugoslav forces between 6 and 11 April. The main Romanian force was at Liubcova, consisting in a battery of 120 mm/L10 naval howitzers in a fortified position. Nearby, there was also a section (2 pieces) of 120 mm/L35 naval howitzers as well as a section of 47 mm light naval guns. The Yugoslavs retaliated with their Air Force. Two Bristol Blenheims raided Arad, badly damaging one of the German fighters stationed there before being both shot down. For its contribution, Romania was rewarded with six ex-Yugoslav aircraft captured by the Germans. These machines, delivered free of charge, were however inoperative. The Romanians cannibalized three of them in order to make the other three operational. The three operational aircraft were all Hawker Hurricanes.