WHEN ARTHUR BRYANT presented the sanitised version of Lord Alanbrooke's diaries in the 1950s, he called the volume that culminated with El Alamein 'The Turn of the Tide'. Winston Churchill, in an observation repeated by Niall Barr in this new history of the decisive phase of the desert war, made the same point. Before Alamein, he said, Britain had almost no victories; after it, there were no defeats. Because of the importance of North Africa to securing control over the Mediterranean, and over the supply lines for the oil needed for armoured vehicles and aircraft, the Allies' feat in driving Rommel out of it was utterly crucial to the outcome of the Second World War. Barr tells us, in precise detail, how this triumph of arms and of morale was achieved.

What distinguishes the military historian from the social or political historian is that the former is required to take us into a world we might find hard to imagine. We can all envisage Churchill at the dispatch box of the House of Commons, or chomping his cigar while walking through