Ukrainian People's RepublicThe 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, four states in post-World War I Europe. The war was the result of the belligerents' desire to expand their territories and their influence over them. Poland, whose statehood had just been re-established by the Treaty of Versailles following the Partitions of Poland in the late 18th century, sought to secure territories it had lost at the time of partitions; the aim of the Soviet states was to control those same territories, which had been part of the Russian Empire until the turbulent events of World War I. The question of victory is not universally agreed on.[1] The Poles claimed a successful defense of their state, while the Soviets claimed a repulse of the Polish eastward invasion of Ukraine and Belarus, which they viewed as a part of the foreign intervention in the Russian Civil War.
The frontiers between Poland and Soviet Russia had not been defined in the Treaty of Versailles and post-war events created turmoil the Russian Revolution of 1917; the crumbling of the Russian, German and Austrian empires; the Russian Civil War; the Central Powers' withdrawal from the eastern front; and the attempts of Ukraine and Belarus to establish their independence. Poland's Chief of State, Józef Piłsudski, felt the time expedient to expand Polish borders as far east as feasible, to be followed by the creation of a Polish-led federation (Międzymorze) of several states in the rest of East-Central Europe as a bulwark against the potential re-emergence of both German and Russian imperialism. Lenin, meanwhile, saw Poland as the bridge that the Red Army would have to cross in order to assist other communist movements and help conduct other European revolutions.
By 1919, the Polish forces had taken control of much of Western Ukraine, emerging victorious from the Polish-Ukrainian War. The West Ukrainian People's Republic had tried unsuccessfully to create a Ukrainian state on territories to which both Poles and Ukrainians laid claim. At the same time, the Bolsheviks began to gain the upper hand in the Russian Civil War and started to advance westward towards the disputed territories causing Petliura's forces to retreat to Podolia. By the end of 1919 a clear front had formed as Petliura decided to ally with Piłsudski. Border skirmishes escalated into open warfare following Piłsudski's major incursion further east into Ukraine in April 1920. He was met by a nearly simultaneous and initially very successful Red Army counterattack. The Soviet operation threw the Polish forces back westward all the way to the Polish capital, Warsaw, while the Ukrainian Directorate fled to western Europe. Meanwhile, western fears of Soviet troops arriving at the German frontiers increased the interest of Western powers in the war. In midsummer, the fall of Warsaw seemed certain but in mid-August the tide had turned again as the Polish forces achieved an unexpected and decisive victory at the Battle of Warsaw. In the wake of the Polish advance eastward, the Soviets sued for peace and the war ended with a ceasefire in October 1920. A formal peace treaty, the Peace of Riga, was signed on 18 March 1921, dividing the disputed territories between Poland and Soviet Russia. The war largely determined the Soviet-Polish border for the period between the World Wars. Much of the territory ceded to Poland in the Treaty of Riga became part of the Soviet Union after World War II, when Poland's eastern borders were redefined by the Allies in close accordance with the British-drawn Curzon Line of 1920.
