Polish–Soviet War

The Polish–Soviet War (February 1919 – March 1921) was an armed conflict between Soviet Russia and Soviet Ukraine against the Second Polish Republic and the Ukrainian People's Republic. It was for control of what is present day Ukraine and parts of present-day Belarus.
A formal peace treaty, the Peace of Riga, was signed on 18 March 1921. It divided the land between Poland and Soviet Russia. Much of the land given to Poland became part of the Soviet Union after World War II.