The Treaty of Riga was signed in Riga, Latvia, on between Poland, Soviet Russia (acting also on behalf of Soviet Belarus) and Soviet Ukraine, ending the Polish–Soviet War (1919–1921). The chief negotiators of the peace were Jan Dąbski for the Polish side and Adolph Joffe for the Soviet side.
Under the treaty, Poland recognized Soviet Ukraine and Belarus, abrogating its 1920 Treaty of Warsaw with the Ukrainian People's Republic. The Treaty of Riga established a Polish–Soviet border about east of the Curzon Line, incorporating large numbers of Ukrainians and Belarusians into the Second Polish Republic. Poland, which agreed to withdraw from areas further east (notably Minsk), renounced claims to the Polish–Lithuanian Commonwealth's border prior to the 1772 First Partition of Poland, recovering only those eastern regions (Kresy) lost to Russia in the 1795 Third Partition. The treaty also addressed matters of sovereignty, citizenship, national minorities, repatriation, and diplomatic and commercial relations. It lapsed with the Soviet Union's invasion of Poland in 1939, and their border was redefined by an agreement in 1945.
World War I removed former state borders across Europe. Following the Russian Revolution which had renounced Tsarist claims to Poland, as well as the Central Powers provisions for Congress Poland in the March 1918 Treaty of Brest-Litovsk, The Great War had ended with the collapse of the Central Powers. The Treaty of Versailles had re-established Poland's independence after a century and a half of being divided by three empires.
The Russian Civil War presented an opportunity for Poland, under the leadership of Józef Piłsudski, to regain parts of the territories of the former Polish–Lithuanian Commonwealth that had been incorporated into the Russian Empire during the Partitions of Poland–Lithuania. In 1920, Piłsudski's initially successful military offensive into Ukraine, whose aim was to establish an independent Ukraine in alliance with Poland, was met with a Soviet counter-offensive into central Poland.