 Complete the following phrase:  The 1st and 3rd Brigades completed their journeys across Russia by October, when they re-entered combat. Between November 20 and December 9, the 1st Brigade fought in the KhopyorDon Operation against the Armed Forces of South Russia, advancing from the Berezovka area to the Don at its tributaries of Boguchar and Rossosh. Meanwhile, the 3rd Brigade defended Petrograd from October to December against the Northwestern Army. As part of the 9th Army, the division headquarters fought against the Armed Forces of South Russia in the areas of Borisoglebsk, Novokhopyorsk, Kalach, and Boguchar in October and November. Between January 3 and 10, 1920, the 21st advanced to Novocherkassk in the 