As Russia collapsed into internal conflict following the October Revolution, the 5th Kargopol Dragoon Regiment moved to Samara in January 1918. In August, Nechaev joined the anti-Bolshevik People's Army of Komuch as commander of the 1st Kazan Cavalry Volunteer Regiment, and became leader of the Kazan Dragoon Regiment in September. Serving as part of Vladimir Kappel's White army (nicknamed "kappelevtsy"), he was eventually appointed head of the Volga Cavalry Brigade in January 1919, and led this unit during several battles of the Eastern Front of the Russian Civil War. He fought at Ufa, Zlatoust, Chelyabinsk, Tobolsk, and Petropavlovsk. The war increasingly turned against the anti-Communist White movement, however, and Kappel's army was forced to retreat into Transbaikal during the Great Siberian Ice March. Though Nechaev survived the retreat, the White army suffered heavy casualties, among them Kappel who died of frostbite and pneumonia.