While Lanz was in command of the defence of Kharkov, he, along with his Chief of Staff Hans Speidel (later chief of staff to Erwin Rommel and involved in the 20 July plot) and Colonel von Strachwitz formulated a plan to arrest Hitler during his scheduled visit to Lanz's headquarters at Poltava.[1][dubious ] To accomplish this, the plotters planned to use von Strachwitz's Großdeutschland Panzer regiment to overpower Hitler's SS bodyguard.[5] This "Plan Lanz" was known in certain military circles, including the leadership of Army Group B, and was even communicated to Field Marshal Erwin Rommel.[5][dubious ] However, on 17 February, when Hitler made his front visit, he chose Manstein's headquarters at Zaporozhye instead of Poltava.[5]