In the long history of the British Army, the Battle of the Somme was its bloodiest encounter. Between July 1 and mid-November 1916, 432,000 of its soldiers became casualties – about 3,600 for every day of battle. German casualties were far fewer despite British superiority in the air and in lethal artillery. What went wrong for the British, and who was responsible? Robin Prior and Trevor Wilson have examined the entire public archive on the Battle of the Somme to reconstruct the day-by-day course of the war. The result is the most precise and authentic account of the campaign on record and a book that challenges almost every received view of the battle. The colossal rate of infantry casualties in fact resulted from inadequate fire support; responsibility for tactical mistakes actually belonged to the High Command and the civilian War Committee. Field-Marshall Haig, the records show, was repeatedly deficient in strategy, tactics, command, and organisation. Hundreds of thousands of soldiers died for a cause that lacked both a coherent military plan and responsible political leadership. Prior and Wilson decisively change our understanding of the history of the Western Front.