Treaty of Trianon

Signed on 4 June 1920 at the Grand Trianon palace in Versailles, the Treaty of Trianon formally ended the state of war between Hungary and most of the Allied and Associated Powers following the collapse of Austria-Hungary at the end of the First World War. It was one of the five Paris Peace Conference treaties, alongside Versailles (Germany), Saint-Germain-en-Laye (Austria), Neuilly (Bulgaria), and Sèvres (Ottoman Empire).

The treaty's territorial provisions were severe. Hungary lost approximately two-thirds of the territory of the pre-war Kingdom of Hungary and about three-fifths of its population. Transylvania and parts of the eastern Banat went to Romania; Slovakia and Carpathian Ruthenia to the newly formed Czechoslovakia; Croatia-Slavonia, Vojvodina, and parts of the Banat to the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia); and Burgenland to Austria. Roughly 3 million ethnic Hungarians found themselves outside the new borders, creating large Hungarian minorities in surrounding states.

Other clauses limited the Hungarian army to 35,000 personnel, prohibited conscription, banned an air force, and imposed reparations obligations whose final amount was left to a later commission. Hungary also accepted "war guilt" language analogous to Article 231 of the Versailles Treaty.

The treaty's legacy has been politically explosive. The slogan Nem, nem, soha! ("No, no, never!") became a rallying cry in interwar Hungary, and revisionism drove Budapest's alignment with Nazi Germany, producing the partial border revisions of the First and Second Vienna Awards (1938, 1940), which were nullified after WWII by the 1947 Paris Peace Treaty. Trianon remains a sensitive issue in Hungarian domestic politics and in relations with Romania, Slovakia, Serbia, and Ukraine; 4 June was designated the Day of National Cohesion by the Hungarian parliament in 2010.