From October to December 1918, he served as a governor general of Tbilisi. During the December Georgian-Armenian war 1918, he was appointed a commander-in-chief and successfully defended the Georgian borders from the troops of General Dro. In 1919 he served as a governor general of Akhaltsikhe and Akhalkalaki and was moved, on 6 October 1920, as a commandant in Tbilisi. During the Soviet invasion of February 1921, he repulsed the Red Army from the Soghanlughi heights at the outskirts of Tbilisi. The war, however, was lost. Mazniashvili did not follow the country’s leaders in exile, but mobilized the remnants of the Georgian armed forces to recover the Black Sea city of Batumi from the Turkish occupation, March 1921. The newly established Soviet government of Georgia declared him outlaw, but later offered him a nominal post in the Red Army.