Political map of Europe & the Mediterranean 4 June 1920 (Treaty of Trianon): Due to the revolutions and invasions that followed the end of the Great War (World War I), it wasn't until 1920 that Hungary was stable enough to sign its peace treaty with the Allies (Treaty of Trianon). The result was a much reduced state that had lost almost three-quarters of its territory and two-thirds of its population to Czechoslovakia, Romania, and Yugoslavia.