The Polish-Soviet War

The Polish–Soviet War (February 1919 – March 1921) was an armed conflict that pitted Soviet Russia and Soviet Ukraine against the Second Polish Republic and the Ukrainian People's Republic over the control of an area equivalent to today's Ukraine and parts of modern-day Belarus. Ultimately the Soviets, following on from their Westward Offensive of 1918–19, hoped to fully occupy Poland, and at some point in the war this appeared possible.

Although united under communist leadership, Soviet Russia and Soviet Ukraine were theoretically two separate independent entities since the Soviet republics did not unite into the Soviet Union until 1922.

Poland's Chief of State, Józef Piłsudski, felt the time was right to expand Polish borders as far east as feasible, to be followed by a Polish-led Intermarium Federation of East-Central European states as a bulwark against the re-emergence of German and Russian imperialisms. Lenin, meanwhile, saw Poland as the bridge the Red Army had to cross to assist other communist movements and bring about other European revolutions. By 1919, Polish forces had taken control of much of Western Ukraine, emerging victorious from the Polish–Ukrainian War. The West Ukrainian People's Republic, led by Yevhen Petrushevych, had tried to create a Ukrainian state on territories to which both Poles and Ukrainians laid claim. At the same time in the Russian part of Ukraine Symon Petliura tried to defend and strengthen the Ukrainian People's Republic, but as the Bolsheviks began to gain the upper hand in the Russian Civil War, they started to advance westward towards the disputed Ukrainian 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 following Piłsudski's Kiev Offensive in April 1920. The Polish offensive was met by an initially successful Red Army counterattack. The Soviet operation threw the Polish forces back westward all the way to the Polish capital, Warsaw, while the Directorate of Ukraine 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 allocated 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 Curzon Line of 1920.

Historical Assessment

Despite the final retreat of Russian forces and annihilation of their three field armies, historians do not universally agree on the question of victory. 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 British military historian and general J.F.C. Fuller ranks the battle of Warsaw in 1920, and the Polish victory in the war, as one of the most decisive victories in history since it prevented Soviet influence from spreading to the borders of Germany, Hungary and Romania at a critical stage in these countries.

https://en.wikipedia.org/wiki/Polish%E2%80%93Soviet_War