Denikin's forces constituted a real threat and for a time threatened to reach Moscow. The Red Army, stretched thin by fighting on all fronts, was forced out of Kiev on 30 August. Kursk and Orel were taken, on 20 September and 14 October, respectively. The latter, only 205 miles (330 km) from Moscow, was the closest the AFSR would come to its target. The Cossack Don Army under the command of General Vladimir Sidorin continued north towards Voronezh, but Semyon Budyonny's cavalrymen defeated them there on 24 October. That allowed the Red Army to cross the Don River, threatening to split the Don and Volunteer Armies. Fierce fighting took place at the key rail junction of Kastornoye, which was taken on 15 November. Kursk was retaken two days later.

Kenez states, "In October Denikin ruled more than forty million people and controlled the economically most valuable parts of the Russian Empire." Yet, "The White armies, which had fought victoriously during the summer and early fall, fell back in disorder in November and December." Denikin's front line was overstretched, while his reserves dealt with Makhno's anarchists in the rear. Between September and October, the Reds mobilized one hundred thousand new soldiers and adopted the Trotsky-Vatsetis strategy with the Ninth and Tenth armies forming V. I. Shorin's Southeastern Front between Tsaritsyn and Bobrov, while the Eighth, Twelfth, Thirteenth, and Fourteenth armies formed A.I. Egorov's Southern Front between Zhitomir and Bobrov. Sergey Kamenev was in overall command of the two fronts. On Denikin's left was Abram Dragomirov, while in his center was Vladimir May-Mayevsky's Volunteer Army, Vladimir Sidorin's Don Cossacks were further east, with Pyotr Wrangel's Caucasian army at Tsaritsyn, and an additional was in the Northern Caucasus attempting to capture Astrakhan. On 20 October, Mai-Maevskii was forced to evacuate Orel during the Orel-Kursk operation. On 24 October, Semyon Budyonny captured Voronezh, and Kursk on 15 November, during the Voronezh-Kastornoye operation (1919). On 6 January, the Reds reached the Black Sea at Mariupol and Taganrog, and On 9 January, they reached Rostov. According to Kenez, "The Whites had now lost all the territories which they had conquered in 1919, and held approximately the same area in which they had started two years before."