Treaty of Trianon
The Treaty of Trianon was an agreement following World War I, which was supposed to regulate the post-war situation of the Hungarian state. It was signed on June 4, 1920, at the Grand Trianon[?] Palace at Versailles, France, reducing the size and population of Hungary by about two thirds. Hungary lost nearly all territories, which were not inhabited solely by Magyar population:
Due to the treaty, Hungary lost its access to the sea and became a landlocked state. Further provisions stated that its army be limited to 35,000 men.
Hungary recovered some of the lost territories at the wake of World War II in 1939-1940, but the new boundaries agreed on at the Treaty of Paris in 1947 were nearly indentical with those of 1920.
see also History of Hungary, Treaty of Versailles