In the week from 7–14 September, Soviet troops were once again reinforced and were preparing for another offensive. The next objectives set by the Stavka were the major cities of Smolensk, Vitebsk and Orsha. The operation resumed on 14 September with the Smolensk-Roslavl offensive operation (Смоленско-Рославльская наступательная операция), involving the left flank of the Kalinin Front and the Western Front. After a preliminary artillery bombardment, Soviet troops attempted to break through the Wehrmacht lines. On the Kalinin Front’s attack sector, the Red Army created a salient 30 km (19 mi) wide and 3–13 km (1.9–8.1 mi) deep by the end of the day. After four days of battle, Soviet rifle divisions captured Dukhovshchina, another "key" to Smolensk.
On the Western Front's attack sector, where the offensive started one day later, the breakthrough was also promising, with a developing salient 20 km (12 mi) large and 10 km (6.2 mi) deep. The same day, Yartzevo, an important railroad hub near Smolensk, was liberated by Soviet troops. On the Western Front's left flank, Soviet rifle divisions reached the Desna and conducted an assault river crossing, creating several bridgeheads on its western shore.
As the result, the Wehrmacht defense line protecting Smolensk was overrun, exposing the troops defending the city to envelopment. General Kurt von Tippelskirch, Chief of Staff of the German 4th Army during the Smolensk operation and later commander of the 4th Army, wrote that:
The forces of the Soviet Western Front struck the left wing of Army Group Center from the Dorogobuzh-Yelnya line with the aim of achieving a breakthrough in the direction of Smolensk. It became clear that the salient—projecting far to the east—in which the 9th Army was positioned could no longer be held.
By 19 September, Soviet troops had created a 250 kilometers (150 mi) long and 40 kilometers (25 mi) wide gap in Wehrmacht lines. The following day, Stavka ordered the Western Front troops to reach Smolensk before 27 September, then to proceed towards Orsha and Mogilev. The Kalinin Front was ordered to capture Vitebsk before 10 October. On 25 September, after an assault-crossing of the northern Dnieper and street fighting that lasted all night, Soviet troops completed the liberation of Smolensk. The same day another important city Roslavl was recaptured. By 30 September, the Soviet offensive force were tired and depleted, and became bogged down outside Vitebsk, Orsha, and Mogilev, which were still held by Wehrmacht troops, and on the 2 October the Smolensk operation was concluded. A limited follow-on was made to successfully capture Nevel after two days of street fighting.