The proclamation of the Republic on 9 November 1918 marked the end of the German Empire and the birth of the Weimar Republic. The following year, Germany's first democratic constitution was enacted. In January 1933, after a decade of political, economic and cultural tensions, Reich President Paul von Hindenburg appointed Adolf Hitler, chairman of the National Socialist German Workers' Party (NSDAP) and “leader” of the strongest parliamentary group in the Reichstag, as Reich Chancellor.

Czechoslovakia was one of the successor states to the Austro-Hungarian Empire and included the territories of today's Czech Republic, Slovakia and Ukraine. On 28 October 1918, the Czechoslovak Republic was proclaimed a free democratic constitutional state based on the Western model. Tomáš Garrigue Masaryk became its first president. Czechoslovakia remained a democratic and comparatively prosperous state until September 1938.

After the First World War and the dissolution of Austria-Hungary, Slovaks and Czechs founded the common state of Czechoslovakia in 1918. The Trianon Treaty finally made Slovakia independent from Hungary after 1000 years under its rule. The Czechoslovak Republic managed to protect the Slovak territories from Hungarian revisionism until 1938, but tensions between Slovaks and Czechs increased, partly because of a centralist government in Prague.

In the end of October 1918 Hungary left the state union with Austria. The new Prime Minister Mihály Károlyi proclaimed the democratic Republic of Hungary on 16 November 1918. Through territorial secessions, Hungary lost about two thirds of its territory to neighbouring states. These territorial losses put a heavy burden on the young government and soon led to its collapse in favour of a short-lived Communist-dominated Soviet Republic under the leadership of Béla Kuns. That regime entered a war against Romania but was defeated and in November 1919 Admiral Miklós Horthy came to power.

On 11 November 1918, Poland was proclaimed as a sovereign state after it had lost independence 120 years ago. Bloody conflicts ensued during the following years over border disputes with neighboring countries. Its constitution established Poland as a parliamentary Republic in March 1921. 1926 Marshall Józef Piłsudski initiated a coup and took power.