This is a thoughtful and important book by a first-rate historian, and deserves to become required reading for those who seek to advance their understanding of the Somme beyond the historiographical trench lines, still disputed, as noisily as pointlessly, by lions and donkeys. It has many great virtues. First among them is the fact that it is a proper history of the battle, not simply an agonising account of its first day extended by a chapter or two to cover the remaining four months’ fighting. Next, it pays as much attention to the French and the Germans as to the British, and considers – for the battle’s impact was not confined to Europe – Australia and Canada too. Among its spot-on judgements is the recognition that on that first terrible day ‘the British did not fail by their own endeavours alone, but in a gruelling fight with a professional, skilled and determined adversary.’ Something in me shrinks from using the phrase ‘learning curve’, as if the rolling downland was graph paper and the all-too-numerous crosses simple measures of combat effectiveness. But it is nonetheless true to say that the growth of British tactical skill and the degradation of German fighting power were two of the Somme’s many interlocking themes.