From March of 1918 to October of 1918 Smidovich served as the chairman of the Moscow Soviet. From 1919 he was the chairman of the Moscow provincial economic council. In 1920 he took part in the Soviet delegation at the peace negotiations with Poland. In 1921 he took part in the liquidation of the Tambov and Kronstadt rebellions. On December 30, 1922, he opened the I All-Union Congress of Soviets , was elected to its presidium. From 1922 he was a member of the Anti-Religious Commission under the Central Committee of the All-Union Communist Party (Bolsheviks) and head of the Secretariat for Religious Affairs, since 1929 Chairman of the Standing Commission on Cults under the Presidium of the All-Russian Central Executive Committee.