Winston Churchill: The World Crisis:
The military conceptions underlying the scheme of attack were characterized by simplicity. The policy of the French and British Commanders had selected as the point for their offensive what was undoubtedly the strongest and most perfectly defended position in the world... writes Sir Douglas Haig:
During nearly two years’ preparation, he [the enemy] had spared no pains to render these defences impregnable. The first and second systems each consisted of several lines of deep trenches, well provided with bomb-proof shelters and with numerous communication trenches connecting them. The front of the trenches in each system was protected by wire entanglements, many of them in two belts forty yards broad, built of iron stakes interlaced with barbed wire, often almost as thick as a man’s finger.
The numerous woods and villages in and between these systems of defence had been turned into veritable fortresses. The deep cellars usually to be found in the villages, and the numerous pits and quarries common to a chalk country, were used to provide cover for machine guns and trench mortars. The existing cellars were supplemented by elaborate dug-outs, sometimes in two storeys, and these were connected up by passages as much as thirty feet below the surface of the ground. The salients in the enemy’s line, from which he could bring enfilade fire across his front, were made into self-contained forts, and often protected by mine-fields; while strong redoubts and concrete machine-gun emplacements had been constructed in positions from which he could sweep his own trenches should these be taken. The ground lent itself to good artillery observation on the enemy’s part, and he had skilfully arranged for cross-fire by his guns.
These various systems of defence, with the fortified localities and other supporting points between them, were cunningly sited to afford each other mutual assistance and to admit of the utmost possible development of enfilade and flanking fire by machine guns and artillery. They formed, in short, not merely a series of successive lines, but one composite system of enormous depth and strength. ‘Behind his second system of trenches, in addition to woods, villages and other strong points prepared for defence, the enemy had several other lines already completed; and we had learnt from aeroplane reconnaissance that he was hard at work improving and that he was hard at work improving and strengthening these and digging fresh ones between them, and still farther back.
All these conditions clearly indicated to the Staffs a suitable field for our offensive, and it was certain that if the enemy were defeated here, he would be more disheartened than by being overcome upon some easier battleground...