Sir William Robertson served as the professional head of the British army and as the constitutional military adviser to both Asquith and Lloyd George from December 1915 to February 1918. This account, based on many new sources, critically examines his leadership of the general staff as the burden of fighting the main body of the German army shifted to the British. This study sheds light on the origins and conduct of the Somme and Passchendaele offensives,...