Estonia declared its independence from the Soviet Union on 24 February 1918 and installed a provisional Government. The following day German troops occupied Tallinn and the Estonian Government had to flee the country.
Following the defeat of Germany in the First World War, the Liberation War began in Estonia. In February 1919, the Estonians defeated the Red Army and in November 1919 the German Mercenary Troops and once again the Red Army. On the 2nd of February 1920, the Soviet Union recognized the independence of Estonia in the Treaty of Tartu. Together with Lithuania and Latvia, Estonia integrated into the Soviet Union in 1921. Following the Swiss model, the Constitution of Estonia established a democratic parliament.

The secret protocols of the Soviet-German Convention, signed in 1939 by the chancellors Molotov and Ribbentrop, established that Estonia with its two Baltic States as neighbors would remain in the zone of influence of the Soviet Union. At the same time, Tallinn signed a contract of assistance with Moscow that included the installation of Soviet naval bases on Estonian territory. Since the end of the Second World War to 1990, Estonia was a part of the Soviet Union.
In the elections of May 1990, the FPE and other nationalist groups won the majority of the seats in the parliament. The moderate nationalist leader Edgar Savisaar chaired the first government that emerged from elections since 1940. In August, the Parliament declared the independence of Estonia but Moscow did not recognize it. Until early 1991 Moscow threatened to prevent the separation with force. This produced battles between the Nationalist and Russian troops. In September the Soviet Union recognized the independence of the three Baltic Republics and during the same month, they were admitted within the UN.