He fought in World War I as the captain of a field engineer company in the Third Siberian Division stationed in Poland.

After he finished his tour, he returned to the Urals in time for the start of the Russian Revolution, in which he fought against the Bolsheviks.

During the Revolution, Molchanov was promoted and put in charge of the Izhevsk brigade and eventually of an entire division in 1918.

After the defeat of Admiral Kolchak's armies and the subsequent Great Siberian Ice March retreat to Transbaikal, Molchanov was appointed the head of the 3rd Separate Rifle Corps of the Far Eastern Army by Ataman Grigory Semyonov.

General Molchanov moved to China, where he served for a brief time under warlord Zhang Zongchang, then to Japan, and in 1923 settled in the United States, where he was interviewed for a lengthy oral history of his life for the University of California's Center for Slavic and East European Studies.