Polish-Soviet War of 1920

The Polish–Soviet war erupted in 1920 in the aftermath of World War I. The root causes were twofold: a territorial dispute dating back to Polish-Russian wars in the 17–18th centuries; and a clash of ideology due to USSR's goal of spreading communist rule further west, to Europe (Soviet westward offensive of 1918–19). At that time both countries had just undergone transition: in 1918 Poland reclaimed independence after 123 years of partitions. In 1917 the October Revolution replaced the liberal, democratic Provisional Government, that had previously displaced the Tsar in Russia, with Soviet rule. The war ended with the Treaty of Riga in 1920, which settled the border issue and regulated Polish-Soviet relations until the German-Soviet invasion of Poland in 1939.

Soviet forces had won a recent series of major victories against the White Russians, defeating Denikin, and had signed peace treaties with Latvia and Estonia. The Polish front, formerly a distraction, became the most important war theater and majority of Soviet resources and forces were diverted into it. In January 1920, the Red Army began concentrating a 700,000-strong force near the Berezina River and in the Belarussian SSR. The Red Army totaled 5,000,000, with additional millions of Russian recruits to draw from, but much of that force was still engaged in the civil war. This number of troops were far less virile than the number of weapons available, and only one in nine soldiers could be properly classified a fighting man. In the course of 1920, almost 800,000 Red Army personnel were sent to fight in the Polish war, of whom 402,000 went to the Western front and 355,000 to the armies of the South-West front in Galicia. The Soviet manpower pool in the West was estimated at 790,000. The Soviets had at their disposal much military equipment left by withdrawing German armies, and modern Allied armaments (including armoured cars, armoured trains, trucks and artillery) captured from the White Russians and the Allied expeditionary forces following their defeat in the Russian Civil War. With the new forces, Soviet High Command planned a new offensive in late April/May.

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