The successor states to the Austro-Hungarian Monarchy
At the latest following the declaration by the USA in June 1918 of its intention to support the liberation of all Slav peoples from the Austro-Hungarian Monarchy, the fate of the Habsburg Monarchy in its original form was sealed. The Czechoslovak Republic was proclaimed on 28 October 1918, the Kingdom of Hungary on 31 October, the Republic of Poland on 10/11 November, and the Kingdom of Serbs, Croats and Slovenes on 1 December. After a short time as a soviet republic, Hungary became a kingdom without a king under Miklós Horthy. Romania, which had signed a treaty of alliance with the Entente in 1916, benefited through the Treaty of Trianon and received not only all the territories with a majority Romanian population but also territories inhabited mainly by Hungarians.