Poplavsky served as the commander of 720th Rifle Regiment (July–September 1941), and then Chief of Staff of 363rd Rifle Division (October 1941 – January 1942). During this time, he participated in the Białystok–Minsk and Smolensk battles. At the beginning of the Battle for Moscow, during the Vyazma and Bryansk defensive operation, his regiment was surrounded. But a few days later, on 6 October, he broke through the encirclement with a battle and withdrew his regiment along with several other units of the 19th Army. For distinctions in the battles of summer and autumn of 1941, he was awarded the Order of the Red Banner.