Meanwhile, "Einsatzkommando" 9 was put to work; they had left Treuburg, in eastern Prussia, and reached Vilna on 2 July. Their main theater of mass killing operations were Grodno and Bielsk-Podlaski (Biala-Podlaska). On 20 July it moved its headquarters to Vitebsk, and then exterminated the citizens of Polotzk, Nevel, Lepel, and Surazh. The command progressed to Vtasma, and from there they killed the communities of Gshatsk and Mozhaisk in the Moscow vicinity. The Soviet counter-offensive forced the "Einsatzkommando" to withdraw to Vitebsk on 21 December 1941. Anticipating the fall of Moscow, the "Vorkommando" Moskau advanced to Maloyaroslavets, earlier captured by the Wehrmacht on 18 October 1941. In practice, "Sonderkommandos" 7a and 7b operated behind the vanguard of the army. The actions were fast, in order to prevent the Jews from escaping the advancing German Army. To the south and east of Smolensk and Minsk, the two "Sonderkommandos" left a wake of dead civilians, from Velikiye Luki, Kalinin, Orsha, Gomel, Chernigov and Orel, to Kursk.