For much of 1942 and early 1943, Army Group Centre was engaged in positional warfare around the Rzhev salient defending against Red Army offensives, collectively known as the Battles of Rzhev. The Soviet forces gained little ground for their losses, especially in the unsuccessful Operation Mars that commenced around the same time as Operation Uranus, the encirclement of the German forces in the Battle of Stalingrad. Kluge's forces were nevertheless depleted and early in 1943, he obtained authorisation to withdraw the 9th Army (General Walter Model) and elements of the 4th Army (General Gotthard Heinrici) from the salient. The resulting Operation Büffel saw the Wehrmacht abandon the salient in phases between 1 and 22 March 1943. The operation eliminated the Rzhev salient shortening the German lines by miles. The withdrawal was accompanied by a ruthless scorched-earth and security campaign, resulting in widespread destruction, razing of villages, deportation of the able-bodied population for slave labour, and killings of civilians by the troops of the Wehrmacht under the guise of "anti-partisan warfare".