In Sarajevo, on 28 June 1914, the Serbian nationalist Gavrilo Princip fired two deadly shots into the Austrian Archduke Franz Ferdinand's car. The assassination created a diplomatic cat's cradle - statesmen, ambassadors and soldiers manoeuvred within a tangle of ambiguous treaties, ill-defined ententes and inflexible military plans. It was a snarl that pleased the warlike and confounded the peaceable; and for a time it paralysed the uncommitted too, not least Britain. In just a month, however, the huge conscript armies of Continental Europe were on the march: the Russians into East Prussia and Austrian Galicia, the Germans towards Paris. But in its haste to knock France out of the war before turning to face Russia, Germany invaded Belgium: a nation whose neutrality Britain was obliged to defend under the terms of an uncertain treaty signed seventy-five years earlier in a very different age. And by the middle of August 1914 the British Expeditionary Force, comprising a hundred thousand regular troops, had arrived in France to fight on the left of the French line. Popular opinion was that this war would be 'over by Christmas', but through the failure of the French high command to comprehend the German military's strength and intentions, 'the Old Contemptibles' of the BEF found themselves standing in the path of an enemy army many times their number, their heroic resistance passed into the annals of war. In this vivid, compelling and rigorously researched new history, Allan Mallinson, one of Britain's foremost military historians and defence commentators, former soldier and author of The Making of the British Army, examines the century-long path that led to war, and the vital first month of fighting in Belgium and France - a conflict of movement before the stalemate of the trenches - and speculates, tantalizingly, on what might have been had wiser political and military counsels prevailed.