This treaty is another good example of the collateral damage to be expected when states join in wars with the express intention of gaining territory, though the war in question has nothing or little to do with them. In the First or Great War of the 20th century, Hungary, because of its alliances with Austria, fought against the Western allies. Romania, sensing a chance to do well out of it, declared for the allies.
The Treaty of Versailles decreed that Hungary, among the states which fought for the loser, Germany, should share the blame and pay the price. After the four terrible years spent mostly advancing and retreating over the trenches were over, Hungary became a Republic, but a Communist revolt established a Communist administration in 1919. This failed, and a monarchical regime (in name only) was introduced with a new constitution, under the leadership of Admiral Horthy.
Hungary’s problems were not solved when in 1920 the Treaty of Trianon was signed which stripped away about one third of her pre-war territory. Romania received almost as much as she had hoped to gain by entering the war on the Allies’ side. Romanians have never been popular with Hungarians, but this was seen as vandalism by the Hungarians, and friendly relations have never been established since. Romania got Transylvania (mixed Romanian and Magyar population), Bessarabia, Cris, and, more importantly, Bukovina and a part of Banat; the rest of the latter went to the Serbs, Croats and Slovenes, which later became most of Yugoslavia. Czechoslovakia gained areas from Hungary, with a mixed population of Magyars and Czechs.
Hungary became a part of the Soviet bloc until 1990 after the fall of Soviet Communism. She joined NATO in 1999 and the European Union in 2004. Romania got her comeuppance when she joined with Axis forces in the 2nd World War, because Soviet forces occupied the entire country in 1944, crippling her physically, mentally and morally. The monarchy was abolished and she lost territory to Russia, Bulgaria and, ironically, Hungary.
In 1991, after the overthrow and subsequent execution of the Communist Ceausescu (and Mrs Ceausescu), Romania became a multi-party democracy. She joined NATO in 2004.