On 12 July the Red Army battled through the demarcation line between the 211th and 293rd divisions on the Zhizdra River and steamed towards Karachev, right behind them and behind Orel. The southern offensive, spearheaded by 4th Panzer Army, led by Gen. Col. Hoth, with three Tank Corps made more headway. Advancing on either side of the upper Donets on a narrow corridor, the II SS Panzer Corps and the Großdeutschland Panzergrenadier divisions battled their way through minefields and over comparatively high ground towards Oboyan. Stiff resistance caused a change of direction from east to west of the front, but the tanks got before encountering the reserves of the Soviet 5th Guards Tank Army outside Prokhorovka. Battle was joined on 12 July, with about one thousand tanks being engaged.