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.
Coastal batteries of Romania
The only time in World War II when the coastal batteries were used in combat was on 26 June 1941, when the Soviet Black Sea Fleet attacked Constanța. The attack was repelled by the Romanian destroyers "Regina Maria" and "Mărășești" supported by coastal artillery, the "Tirpitz" battery damaging the Soviet destroyer leader "Kharkov".