The end of World War I brought about important changes in the whole of Europe. One of them – for Poles, the most crucial one, received with incredible enthusiasm – was Poland’s return to the political map of the continent, after 123 years of partitions. The most urgent challenge facing the reborn state was to mark out its borders, including with Soviet Russia. Germany’s capitulation saw the withdrawal of German troops from lands belonging to the Polish-Lithuanian Commonwealth before the partitions – including Courland, Wilno and Białystok. Already on 16 November 1918, the Bolshevik army command formed the Western Army, whose tasks included taking over land abandoned by the Germans. At the same time, self-defence units were spontaneously formed there against the Bolsheviks. These were voluntary military formations whose purpose was to incorporate the borderlands into the Polish state. On 29 December 1918 these units were incorporated into the Polish Army. The Poles aspired to mark out the eastern border, at the same time intending, in keeping with Józef Piłsudski’s federal conception, to create an international anti-Bolshevik front. At this same time, the Communists intensified their operations not only ideologically and politically, but also militarily. The revolution in Germany was continuing, and in the spring of 1919 the Hungarian Soviet Republic and the Munich Soviet Republic were proclaimed. There is no doubt that Soviet imperial plans assumed a further expansion of the Communist revolution westwards, but Poland stood in the way of their implementation. A conflict was inevitable.
On 14 February 1919 the first clashes broke out in Mosty between the Red Army and Polish units. In April the Polish Army launched a counteroffensive, recapturing Wilno and Nowogródek (Navahrudak), and, in August, Mińsk. In autumn 1919, Polish troops halted at the Berezina line. At the same time, Polish-Bolshevik peace negotiations had been in progress since July 1919, but ended in failure in December that same year. On 25 April 1920 a Polish preventive strike was launched, known as the Kiev Offensive. Its purpose was to interrupt and paralyse Soviet war preparations, preserve Poland’s independence and pave the way for an independent Ukraine to be proclaimed. Despite initial success – the seizure of Kiev (7 May 1920) – the operation failed. A counter-strike by the Bolsheviks on 14 May strongly engaged the Polish forces and created conditions for a decisive Soviet counter-attack in the south. On 5 June 1920 the Polish forces started retreatin. On 4 July 1920 a general offensive of the Soviet Western Front began, which took the Bolsheviks to the outskirts of Warsaw from the northern side. The South-Western Front conducted war operations in the south. The Soviet plan to take Warsaw assumed that the Vistula would be forced by the main forces from the north and one army from the south. After crossing the river, the combined forces were to attack the capital from the north- and south-west. On 10 August, after an offensive lasting six weeks, the Soviets reached the Mława – Przasnysz – Wyszków – Węgrów – Siedlce line. However, the Warsaw bridgehead was the main thrust of the operations. The Northern Front commanded by Józef Haller operated along the stretch from the border with East Prussia to the mouth of the Wieprz River by Dęblin. The troops grouped along it were to engage the Soviet forces in long-lasting defensive fighting and prevent them from controlling Warsaw. General Władysław Sikorski’s 5th Army was positioned on the northern stretch of that front, along the Wkra River to Pomiechówek. Warsaw’s outskirts – the central stretch of the front – were being defended by General Franciszek Latinik’s 1st Army, spread out from Zegrze to Karczew. Its main task was the direct defence of the capital and its eastern bridgehead. The southern stretch of the front, from Góra Kalwaria to Dęblin, along the Vistula’s western bank, was occupied by General Bolesław Roja’s 2nd Army. General Edward Rydz-Śmigły’s Central Front, positioned from Dęblin to Brody along the Wieprz River, was to attack the flank and rear of Tukhachevsky’s forces when they engaged in battle with General Haller’s troops. This front was composed of the lower Wieprz force comprising General Leonard Skierski’s 4th Army and the upper Wieprz force personally commanded by Rydz-Śmigły, concentrating part of General Zygmunt Zieliński’s 3rd Army. The Polish Southern Front headed by General Wacław Iwaszkiewicz was spread out to the south of Brody as far as the Dniester River. The Polish forces intended for the decisive battle with Tukhachevsky’s troops comprised, in five armies, about 120,000 infantry and artillery units, 9,000 cavalry and 630 cannons. On the morning of 13 August 1920 the Red Army’s strike on Polish positions near Radzymin was the start of the battle for Warsaw. The attack was repelled, but in the afternoon Bolshevik units launched a coordinated attack on the defensive positions at Radzymin, Wołomin and Ossów. Radzymin fell that same evening, as did Ossów the following day. The Soviets broke through the first defensive line of the Praga bridgehead and headed in the direction of Praga. In order not to allow enemy units to surge through the breach in the Polish defence, generals Rozwadowski and Haller ordered an immediate offensive by General Sikorski’s 5th Army from the Wkra River. Its purpose was to stop the Red Army at the positions it was occupying and to prepare conditions to form the Polish defence at the Praga bridgehead. At noon on 14 August the 5th Army attacked from the Wkra line in the direction of Nasielsk as well as Nowe Miasto and Płońsk. The attacks in the first two directions ended in a fiasco. On the morning of 15 August the Soviets broke through the front in the region of Borków, with the Poles suffering great losses. In the north, in the direction of Płońsk, the situation of the Polish forces was much better. Intense fighting by the Wkra River on 14 and 16 August failed to produce any significant breakthroughs on the northern flank of General Haller’s front. The 5th Army maintained its positions and even pushed them eastwards, at the level of Nasielsk. However, important changes were taking place at the Praga bridgehead. On 14 August the Poles retook Ossów. The symbol of this battle was Father Ignacy Skorupka, the heroic chaplain of the 236th Volunteer Army Infantry Regiment. On the evening of 15 August the Poles regained Radzymin as well as their lost defensive positions. Three days earlier Józef Piłsudski had left Warsaw to take direct command of a manoeuvre strike force by the Wieprz River. The Marshal had planned to start the offensive on 17 August, but after hearing about the defeats near Radzymin he decided – despite his doubts – to move the date for starting the offensive turnabout forward to 16 August. For the planned manoeuvre to succeed, rapid action was necessary, as was using the element of surprise against the enemy. Early on the morning of 16 August a Polish counter-strike was launched against the flank and rear of the Red Army forces fighting for Warsaw. Between the evening of 17 and 18 August, units of the Polish strike force reached the Warsaw – Mińsk Mazowiecki – Brześć (Brest) highway, breaking through the Bolshevik forces’ main line of communication. The Soviets’ orderly retreat soon became a chaotic flight of panic. Soldiers ditched their heavy equipment and many of them broke away from their ranks to form marauding groups. The Bolshevik forces were definitively broken up at the Neman River. From 20 to 28 September the Poles attacked the Soviets along the entire front. The fiercest combats occurred around Grodno, Brzostowice and Wołkowysk. The fighting ended with a pursuit after the enemy. On 12 October 1920 a ceasefire was signed, and on 18 March 1921 a peace treaty was concluded establishing the borders between Poland and Soviet Russia and regulating relations between the two countries.