In the wake of the Russian westward offensive of 1918–1919 and of a series of escalating battles which resulted in the Poles advancing eastward, on 21 April 1920, Marshal Piłsudski (as his rank had been since March 1920) signed a military alliance (the Treaty of Warsaw) with Ukrainian leader Symon Petliura to conduct joint operations against Soviet Russia. The goal of the Polish-Ukrainian treaty was to establish an independent Ukraine and independent Poland in alliance, resembling that once existing within Polish-Lithuanian Commonwealth In return, Petliura gave up Ukrainian claims to western lands of Galicia being a historical part of the Crown of Poland, for which he was denounced by Ukrainian nationalist leaders.
The Polish and Ukrainian armies, under Piłsudski’s command, launched a successful offensive against the Russian forces in Ukraine. On 7 May 1920, with remarkably little fighting, they captured Kiev.
Piłsudski (left) and Edward Rydz-Śmigły (right), 1920, during Polish-Soviet War
The Bolshevik leadership framed the Polish actions as an invasion; in response, thousands of officers and deserters joined the Red Army, and thousands of civilians volunteered for war work. The Soviets launched a counter-offensive from Belarus and counter-attacked in Ukraine, advancing into Poland in a drive toward Germany to encourage the German Communist Party in its struggle to take power. . . . Yet over the next few weeks, Poland’s risky, unconventional strategy at the August 1920 Battle of Warsaw halted the Soviet advance.
Treaty of Warsaw (1920)
Piłsudski was looking for allies against the Bolsheviks and hoped to create a Międzymorze alliance; Petliura saw the alliance as the last chance to create an independent Ukraine.
Piłsudski also wanted an independent Ukraine to be a buffer between Poland and Russia rather than seeing Ukraine again dominated by Russia right at the Polish border. Piłsudski, who argued that “There can be no independent Poland without an independent Ukraine”