In his book, "", Bernard Cornwell summarizes the opinions of several historians that Soult's presence in the Army of the North was one of several factors contributing to Napoleon's defeat, because of the animosity between him and Marshal Michel Ney, the other senior commander, and because, in spite of his experience as a soldier, Soult lacked his predecessor Marshal Louis-Alexandre Berthier's administrative skills. The most glaring instance of this was his written order, according to Napoleon's instructions, to Marshal Emmanuel de Grouchy to position his force on the British Army's left flank in order to prevent reinforcement by the Prussians. Cornwell decries the wording of Soult's order as "almost impenetrable nonsense", and Grouchy misinterpreted the order, instead marching against the Prussian rearguard at Wavre.