The clans kept arriving. Every day saw new battalions and new guns disembark. England was sending to Sir Douglas Haig men and material, but not an army in the modern sense. He had to weld the consignments into a whole there in the field in face of the enemy. Munitions were a matter of resource and manufacturing, but the great factory of all was the factory of men. It was not enough that the gunners should know how to shoot fairly accurately back in England, or Canada, or Australia. They must learn to cooeperate with scores of batteries of different calibers in curtains of fire and, in turn, with the infantry, whose attacks they must support with the finesse of scientific calculation plus the instinctive _liaison_ which comes only with experience under trained officers, against the German Army which had no lack of material in its conscript ranks for promotion to fill vacancies in the officers' lists. From seventeen miles of front to twenty-seven, and then to sixty and finally to nearly one hundred, the British had broadened their responsibility, which meant only practice in the defensive, while the Germans had had two years' practice in the offensive. The two British offensives at Neuve Chapelle had included a small proportion of the battalions which were to fight on the Somme; and the third, incomparably more ambitious, faced heavier concentration of troops and guns than its predecessors. What had not been gained in battle practice must be approximated in drill. Every battalion commander, every staff officer and every general who had had any experience, must be instructor as well as director. They must assemble their machine and tune it up before they put it on a stiffer road than had been tried before. The British Army zone in France became a school ground for the Grand Offensive; and while the people at home were thinking, "We've sent you the men and the guns--now for action!" the time of preparation was altogether too short for the industrious learners. Every possible kind of curriculum which would simulate actual conditions of attack had been devised. In moving about the rear the rattle of a machine gun ten miles back of the line told of the machine gun school; a series of explosions drew attention to bombers working their way through practice trenches in a field; a heavier explosion was from the academy for trench mortars; a mighty cloud of smoke and earth rising two or three hundred feet was a new experiment in mining. Sir Douglas went on the theory that no soldier can know his work too well. He meant to allow no man in his command to grow dull from idleness. Trench warfare had become systematized, and inevitably the holding of the same line for month after month was not favorable to the development of initiative. A man used to a sedentary life is not given to physical action. One who is always digging dugouts is loath to leave the habitation which has cost him much labor in order to live in the open.