The ready adaptation of the Allies to the new exigencies of war forced the Germans to rush to earth. There came a change so sudden that it seemed as if one had jumped literally from one century to another. "We have driven them underground," said M. Paul Deschanel, the eloquent President of the Chamber. But after they sank into the earth the Germans still made desperate efforts to escape Bloch's conclusion: that immobility which he predicted as being the inevitable result of the conflict of armed nations. They endeavoured by their inventive genius to break that immobility. By asphyxiating gas, by liquid fire, by aerial warfare (especially against England), did they seek, as Mr. Wells points out, to create, such diversion as would avoid so barren a conclusion to armed effort.

With the second phase of the battle the pulsing, stirring features of the old warfare largely disappeared. There was no longer the crowded rustle of the ranks, except when men crept in the semi-darkness from their trenches and attacked in the open against barbed wire and murderous missiles. The long, sinuous line of red, with its sheen and shimmer of weapons glancing back the sun, gay plumes to give a nodding note of youth, almost of feminine finery, had passed to the limbo of military museums and the pages of the historians of past battles. None of these things; instead, men in musty garments, covered with dust in summer or the mud of winter rains, and, in place of the cavalry charge in the open, the terrible twilight war began. Those who waged it shirked the daylight, dwelt in pits and crouched in dark ramparts as if the sight of God's good sun shamed them. Gone was the brave display riotous in colour and glory, glittering from ten thousand points. In its place was a lone and dismal landscape, a drab expanse of trenches interminably long; of furrows deeply drawn through the earth hiding living grain in their depths. Singular country, like some vast cemetery, stretching indefinitely towards a dull horizon dead in its outer aspects, and yet hiding in its bowels the quick and the dead, the living happily outnumbering those who live no more. Of course, the great novelty of the war was its vast length of front. In France it stretched from the North Sea to the rocky ramparts of Switzerland, 700 kilometres across the fair land of France; and if one counted all the ramifications and convolutions, then 10,000 kilometres represented the sum of this amazing and ceaseless industry which turned soldiers into navvies; moreover, this trench warfare was universal where fighting occurred, and was not special merely to Belgium and France, for it existed in Russia, in Mesopotamia, and the Balkans. A French Army Corps numbers 35,000 men, and, taking the general character of the ground, the parts that can be naturally defended with those that require barricades of barbed wire and other obstacles to reinforce their strength, this Army Corps can hold a line of ten kilometres. Thus 2,000,000 men is about the normal garrison of a line of 500 kilometres. But it must not be supposed that the lines are uniform; they vary considerably. For instance, where the ground is steep and rocky, the defence is rendered easier and the guards of the first trench may be less numerous than in cases where the conditions are more favourable to attack. But such matters are settled by the local commandant, who takes into consideration all the conditions and makes his dispositions accordingly. There are parts of the line where it is not necessary to place men because the parts are enfiladed by cannon, and other places where every mechanical means has been resorted to for strengthening the trenches. The telephone is largely used, and is linked with advanced posts, called postes d'écoute, where the observer can note the least activity in the enemy's trenches. Thus the men guarding the first-line trenches can be sensibly reduced, leaving a greater proportion to remain in the second-line trenches and in rest chambers dug out of the earth at the ends of the lines. Of course, the trenches vary considerably, and the commander takes note of the character of the soil. He makes use of a hill-side, even of the ditches with embankments on the side of the road, of every natural conformation of the soil, and the number of men necessary to defend the line varies according to these circumstances.

It is true, certainly, that trench warfare has inflicted a great loss of the picturesque, of glittering movements, of kaleidoscopic effects which turned and twisted into wonderful pictures; the picture to-day is replaced by a melancholy waste of earth scored and humped into mounds.

Within was life, and no end to labour, for there were trenches, always more trenches to be dug as the line swayed or curved in new forms, yielding to pressure or being broken by it. And in the trenches themselves there was a perpetual search for improvement, and the longer the troops stayed there, the more highly organised became their abodes. If there was not an abundance of hot water there was generally enough of cold, and gas on every floor; alas! too much of it. There were wooden floors and wooden walls and pictures, and even sculpture adorned them. In these subterranean passages dwelt our men in a kind of heroic enjoyment Of a battle without issue, of a sort of deadly ding-dong, only varied by the blackening of the sky with the monstrous smoke of projectiles that count a man a mere atom in their whirlwind path—fearful engines that lay waste the country, that reduce villages to a hopeless jumble of stones and bent iron and splintered wood, with derisive-looking chimneys floating in a troubled sea, like derelicts in the track of a tornado.

It was clear that in this squatting war all traditions had crumbled hopelessly and wilted away. The monstrous engines belched fire and destruction. From the caverns themselves, deeply cut in the once fertile fields, issued a storm of shot and shell from machine-guns, from mortars of an old-fashioned type, from cannon of the newest type—every imaginable engine of destruction, down to the old hand-grenade, again in usage from a distant past—a past so ancient that Scott reminds us in Rob Roy that "in those days this description of soldiers" (i.e. the Grenadiers) "actually carried that destructive species of firework from which they derive their name." Thus every device known to man's inventive and destructive brain was directed into a new and diabolical channel, and from time to time the vast engines employed emitted a rending noise as if the earth were spitting flame and its rocky ribs had shattered into quivering fragments—a volcano in its most fearful mood, sending forth a mad jumble of rocks and a living stream of lava devastating and devouring.

A gaunt and desolate country haunted by the melancholy crows, resounding with clacking detonations of fusillades and a hoarse bass of heavy cannon, is the place of invisible war. One rubs shoulders with it without being aware of it. One comes suddenly upon it in all innocence. A journalistic friend, at the beginning of the war, dashed into its area all unknowing that he had come on top of it. To his unpractised eye the lines were no more clearly marked than the Equator or the North Pole. And, of course, every effort is made to conceal the battle-field. Beet-root grows riotously on battlements, guns hide behind trees and are covered with branches, so that the airman, peering from his height, sees nothing but the flicker of leaves. The line hides itself as soon as it fights, and without loss of time prepares against a possible retreat. That is the method of it. Should it be driven back, there are strong positions in the rear for the rallying, for the defence à outrance, and for the counter-attack. Fronts have two or three lines of shelter trenches, deep enough to cover a man and generally a yard in width. These trenches are proportioned to the effectives employed. They contain redoubts and blockhouses where guns are placed; they are linked by zigzag paths, and, as a last resort, with a trench of cement, a veritable fortress where are cannon as well as machine-guns. These covered over and fortified trenches nearly always contain rest chambers and magazines for rifles and the different sorts of ammunition required.

The lesson of this trench warfare, therefore, is that if a combatant retires before it is too late he has every chance to survive to fight another day; and he has all the more chance of a new offensive, or at least of maintaining a strong defensive, if he retires in the direction of his resources, or what is called his line of operation, whence he receives his munitions, food and material of war. He retires from the battle, therefore, at the psychological moment when he sees he is likely to be overwhelmed, and reconstitutes himself in the rear. The opening phases of 1914 gave us two parallel retreats: from the Belgian frontier to the Seine by the Allies, and from the Marne to the Aisne by the Germans. The campaign in Poland also showed a similar disposition, and the Russians reformed their line and beat the Germans after they retreated before them. Therefore a mere retreat may be, literally, little more than a strategic movement in the rear. It does not mean, certainly, that all is lost or that the position of the retreating force is one of utter hopelessness.

After the opening phases of the war, the subterranean character of the fighting was maintained, until such big offensives as Verdun re-evoked the old-time battle, when the Kaiser watched the operations from an eminence, and on a front of twenty miles scenes of the old onslaught were re-enacted. But in this case the initiative was left to the Germans. To them also the greater part of the losses, for whilst they manoeuvred in the open and hurled masses of their grey-green warriors upon the French trenches, the defenders enfiladed the masses and mowed them down with the gigantic scythes that their science had forged since the war began.

A curious feature of the fighting in the Great War was the element of fatigue. We have met with it everywhere. It follows closely the course of the war; it is seen in every phase. At Charleroi and Mons and those terrific fights that marked the beginning of the war, the retreating armies of England and France escaped because of the exhaustion of the Germans. If cavalry had harried their rearguards and mobile cannon had cannonaded their flanks the retreat might have been turned into a rout. For the French, largely composed of reservists, were within an ace of demoralisation. And again the Allies, as conquerors, showed extreme fatigue in the battle of the Marne, when the victory might have been more decisive had it been followed up by unwearied troops, or, again, by masses of cavalry.

The cavalry, indeed, of both combatants proved singularly ineffectual, and, as I have just pointed out, failed as a means of attack or to pursue retreating armies; and an interesting feature was the dismounting of the cavalry and its employment as infantry in the trenches. Cavalrymen were divorced from their horses and given infantry guns; and their equipment and appearance approached very nearly that of the foot-soldier. The Cuirassiers, for instance, took off their picturesque manes and removed the top pieces of their helmets, and thus very nearly imitated the bourguinet, or low, mediaeval-looking helmet of the French infantry. Even reconnaissance, the old duty of the cavalry, has been undertaken by the aeroplane; and the horse-soldier, indeed, has little place in modern warfare. Some experts, however, hold that a new rôle has emerged from the war which the cavalry is qualified to fill. It consists in their employment in large forces flanked by mobile cannon and cyclists, whereby their offensive radius is greatly extended.