Polish–Soviet War

In the chaos that followed the First World War, the newly independent Polish state and Bolshevik Russia fought for control of the borderlands between them, the lands of today's Lithuania, Belarus and Ukraine. The fighting began early in 1919, grew into full-scale war in 1920, and ended with a ceasefire in October 1920 and the Peace of Riga in March 1921. Poland's victory before Warsaw in August 1920 halted the westward advance of the Red Army, and the settlement fixed Poland's eastern frontier until the Second World War.

After Germany's defeat, Soviet Russia under Vladimir Lenin annulled the Treaty of Brest-Litovsk and sent forces west into the areas the German army was leaving. Lenin saw Poland as a bridge for carrying revolution into Europe. Polish leaders, above all the chief of state Józef Piłsudski, wanted to push Poland's border far to the east, ideally within a federation of states recalling the old Polish–Lithuanian Commonwealth. The Red Army took Vilnius on 5 January 1919, and through 1919 Polish forces advanced into Lithuania and Belarus, taking Minsk on 8 August, while also defeating the West Ukrainian republic in eastern Galicia.

In December 1919 the Allied Supreme War Council proposed a provisional eastern boundary for Poland, a version of which later became known as the Curzon Line.

By 1920 the Red Army, having defeated many of its enemies in the Russian Civil War, could turn west. On 21 April 1920 Piłsudski allied with Symon Petliura, leader of the Ukrainian People's Republic, and later that month launched an offensive into Ukraine. Polish and Ukrainian troops took Kiev on 7 May, but the Soviet armies there escaped destruction, and the expected Ukrainian support did not materialise.

In June Semyon Budyonny's 1st Cavalry Army broke through the Polish front in Ukraine, and in the north Mikhail Tukhachevsky's armies drove rapidly across Belarus. Polish troops left Minsk on 11 July. The same day the British foreign secretary, Lord Curzon, asked the Soviets to halt at the line that now bore his name, but the advance continued, and on 23 July the Soviets set up a Polish revolutionary committee to govern captured Polish territory. By August Soviet forces were approaching Warsaw, while to the south Budyonny, encouraged by Joseph Stalin, pressed towards Lwów instead of supporting Tukhachevsky.

Between 12 and 25 August 1920 the Poles turned the war around. Defenders held the approaches to the capital, notably at Radzymin, while Piłsudski led a counter-attack from the Wieprz river into the exposed flank and rear of Tukhachevsky's armies, a plan devised with his chief of staff Tadeusz Rozwadowski. The Soviet forces fell back in disorder. Poles call the victory the "Miracle on the Vistula". Further victories followed at Komarów on 31 August, where Budyonny's cavalry was beaten, and on the Niemen river in late September.

Both sides now accepted that neither could win outright. A ceasefire took effect on 18 October 1920, and the Peace of Riga was signed on 18 March 1921. It divided the disputed lands, placing Poland's frontier about 200 kilometres east of the Curzon Line and giving it western Ukraine and western Belarus, while Soviet Ukraine and Soviet Belarus were recognised. Piłsudski's plans for a federation came to nothing.

Casualty estimates run to more than 200,000 on each side. Prisoners suffered badly: by one account, between 16,000 and 20,000 of some 80,000 to 85,000 Soviet prisoners died in Polish camps, and about 20,000 of 51,000 Polish prisoners died in Soviet hands. Polish and Russian historians each tend to claim victory, and some writers see a Polish military success paired with political disappointment. The border lasted until the Soviet invasion of 1939, and at the Yalta Conference in 1945 the Allies agreed a frontier close to the Curzon Line. Under communist rule the war was largely left out of Polish history books.

Our 1920 map shows the region in the year of the main campaigns, and our 1930 and 1938 maps show the Riga frontier of interwar Poland with the Soviet Union.