May 9, 1920:
The Polish army led by General Edward Rydz-Śmigły celebrates its capture of Kiev with a victory parade on Khreschatyk Street.
The Polish-Soviet War’s roots lay in the Treaty of Versailles, which was one of the peace treaties at the end of World War I. The borders between the USSR and Poland were vaguely defined in the document.
By late 1919 both Polish Chief of State Józef Piłsudski and Soviet chairman Vladimir Lenin had tried to expand their borders into the Ukraine. The Poles had taken control of much of the west of the country after their victory in the Polish-Ukrainian War, while the Bolsheviks had invaded the eastern part of the Ukraine, where Symon Petliura’s forces had tried to defend the fledgling Ukrainian People’s Republic.
By the end of the year, Petliura had allied with Poland, and the latter country had made a major incursion into eastern Ukraine in 1920, launching the war.
In the summer of 1920, the Soviets looked set to defeat the Poles, and nearly took Warsaw, but the Poles emerged victorious, and the Soviets pressed them for peace. A ceasefire was signed in October of that year, and a formal treaty, the Peace of Riga, was signed in 1921.
The treaty divided the disputed territories between Poland and the USSR, and set the Soviet-Polish border between World War I and II.
Above, Polish soldiers in Kiev.