 Zabecki notes that Rommel's brilliant tactical moves were logistically unsustainable, which eventually led to a strategic defeat.General Klaus Naumann, who served as Chief of Staff of the Bundeswehr, agrees with Charles Messenger that Rommel had challenges on the operational level, and states that Rommel's violation of the unity of command principle, bypassing the chain of command in Africa, was unacceptable.Some historians, such as Zabecki and Peter Lieb, also take issue with Rommel's absence from Normandy on the day of the Allied invasion, 6 June 1944.