In December 1917 Sablin led the 1st Moscow Revolutionary formation to the Southern Russia and Ukraine. Taking charge of the northern segment of the Southeastern front, he participated in taking the city of Novocherkassk. In 1918 he became a commissar of the Western curtail of Moscow district. The same year Sablin participated in the Left SR uprising due to which he was convicted by a revolutionary tribunal to a year in prison and was detained in Saratov on 16 July 1918. He however was soon amnestied by the All-Russian Central Executive Committee and in December 1918 headed the Kupyansk revkom.