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.
Geography of Romania
Romania's exterior boundaries are a result of relatively recent events. At the outbreak of World War I, the country's territory included only the provinces of Walachia, Moldavia, and Dobruja. This area, known as the Regat or the Old Kingdom, came into being with the disintegration of the Ottoman Empire in the mid-nineteenth century. At the end of World War I, Romania acquired Transylvania and the Banat. Some of this territory was lost during World War II, but negotiations returned it to Romania. Although this acquisition united some 85 percent of the Romanian-speaking population of Eastern Europe into one nation, it left a considerable number of ethnic Hungarians under Romanian rule. Disputes between Hungary and Romania regarding this territory would surface regularly, as both considered the region part of their national heritage. Questions were also periodically raised as to the historical validity of the Soviet-Romanian border. Bukovina and Bessarabia, former Romanian provinces where significant percentages of the population are Romanian-speaking, were part of the Soviet Union from the end of World War II to its dissolution, and subsequently part of the (formerly Soviet) states of Ukraine and Moldova. Despite ongoing and potential disputes, however, since 1989 Romania has no territorial claims to make.