The defences having increased in strength and depth, the blow would require to be more powerful, precise, and concentrated as to space and time. After the attacks of September, 1915, the French Staff set down as an axiom that "material cannot be combatted with men." Consequently, no more attacks without thorough preparation; nothing was to be left to chance. The orders issued to the different arms, divisions, battalions, batteries, air-squadrons, etc., were recorded in voluminous plans of attack, the least of which numbered a hundred pages. Thousands of aerial photographs were taken and assembled; countless maps, plans and sketches made. Everything connected with the coming drama was methodically arranged: the staging, distribution of the parts, the various acts. Such was the intellectual preparation which, lasting several months, was carried out simultaneously with the equipping of the front line. Equipping the Front Line Preparing for a modern battle is a Herculean task. At a sufficient distance behind the front line immense ammunition and revictualling depôts are established. Miles of railway, both narrow and normal gauge, have to be put down, to bring up supplies to the trenches. Existing roads have to be improved, and new ones made. In the Somme, long embankments had to be built across the marshy valleys, as well as innumerable shelters for the combatants, dressing-stations, and sheds for storing the ammunition, food, water, engineering supplies, etc. Miles of deep communicating trenches, trenches for the telephone wires, assembly trenches, parallels and observation-posts had to be made. The local quarries were worked, and wells bored. [Illustration: _Ginchy, bombarded by the British on July 11, 1916._] [Illustration: _Ginchy, ten days later (July 21, 1916)._] [Illustration: _Ginchy, two days before capture by the British (Sept. 7, 1916). See p. 86._ ILLUSTRATING THE PROGRESSIVE DESTRUCTION AND LEVELLING OF A VILLAGE BY ARTILLERY.] [Illustration: FIRING A 12-INCH LONG-RANGE GUN.] The Part Played by each Arm in the Different Phases of the Attack In modern, well-ordered battle, it is the material strength which counts most. The cannon must crush the enemy's machine-guns. Superiority of artillery is an essential element of success. According to the latest formula, "the artillery conquers, the infantry occupies." At each stage of the battle, each arm has a definite role to play. The Artillery _Before the battle_, the artillery must destroy the enemy's wire entanglements, trenches, shelters, blockhouses, observation-posts, etc.; locate and engage his guns; hamper and disperse his working parties. _During the battle_, it must crush enemy resistance, provide the attacking infantry with a protecting screen of fire, by means of creeping barrages, and cut off the defenders from supplies and reinforcements by isolating barrages.