As the Polish–Soviet War grew in intensity, in late April 1920 the Red Army of Russia's new Soviet regime pushed back Polish forces and invaded Poland. Subsequently, Sikorski successfully defended Mozyr and Kalenkowicze until 29 June, but later failed to hold the Brest fortress, although he defended it long enough to allow the Polish forces in the region to retreat in an orderly manner. On 6 August he was named the commander of the newly formed Polish 5th Army, which was tasked with holding the front to the north of Modlin, between Narew and Wkra rivers. He distinguished himself commanding the 5th Army on the Lower Vistula front during the Battle of Warsaw. At that time Soviet forces, expecting an easy final victory, were surprised and crippled by the Polish counter-attack. During that battle (sometimes referred to as "the Miracle at the Vistula") Sikorski stopped the Bolshevik advance north of Warsaw and gave Piłsudski, the Polish commander-in-chief, the time he needed for his counter-offensive; beginning with the 15 August his forces successfully engaged the Soviet 5th and 15th Armies. After the Battle of Warsaw, from 30 August, Sikorski commanded the 3rd Army. His forces took Pińsk, and fought during the latter stages of the Battle of Lwów and the Battle of Zamość, and then after Battle of Niemen advanced with his forces toward Latvia and deep into Belarus. The Poles defeated the Soviets, and the Polish–Soviet Treaty of Riga (March 1921) gave Poland substantial areas of Belarus and Ukraine's (Kresy). Sikorski's fame was enhanced as he became known to the Polish public as one of the heroes of the Polish–Soviet War. He also kept publishing military science articles during the war itself. For his valorous achievements Sikorski was promoted to divisional general on 28 February 1921, and was awarded Poland's highest military decoration, the order of Virtuti Militari, on 15 March that year.