Leading Whitehall historian Peter Hennessy examines Britain's secret war planning and preparations before 1914. Drawing on official papers, sound archive, and interviews with historians, Hennessy discusses what was in the minds of Asquith, ministers, officials and top soldiers and sailors, as they prepared for a possible conflict and as they finally took Britain into war in August 1914. He explores tensions between senior military and naval officers, between the Admiralty and the War Office, and within the Cabinet, and shows how debates and divisions shaped the war plans and influenced their effectiveness.