The particular titles of corps are of no great value in following the leading main lines of a military movement; but it may be worth remembering that this "number 5," to which von Kluck had allotted the turning movement, was the _Second_ German Corps. With its cavalry it numbered alone (and apart from all the other forces of von Kluck which were engaging the British line directly) quite three-quarters as many men as all that British line for the moment mustered. It was not possible, from local circumstances which the full history of the war, when it is written, will explain, for the British contingent to fall back in the remaining hours of daylight upon that Sunday. Belated by at the most twelve hours, as the news of the French retirement had been, the British retirement followed it fully twenty hours after. It was not until daylight of Monday, the 24th, that all the organizations for this retirement were completed, the plans drawn up, and the first retrograde movements made. To permit a retirement before such a great superiority of the enemy to be made without disaster, it was necessary to counter-attack not only at this inception of the movement, but throughout all the terrible strain of the ensuing eight days. Here it may be necessary to explain why, in any retirement, continual counter-attacks on the pursuing enemy are necessary. It is obvious that, under equal conditions, the pursuing enemy can advance as fast as can your own troops which are retreating before him. If, therefore, a retreat, once contact has been established, consisted in merely walking away from the enemy, that enemy would be able to maintain a ceaseless activity against one portion of your united force--its rear--which activity would be exercised against bodies on the march, and incapable of defence. To take but one example out of a hundred: his guns would be always unlimbering, shooting at you, then limbering up again to continue the pursuit; unlimbering again, shooting again--and so forth; while your guns would never reply, being occupied in an unbroken retirement, and therefore continually limbered up and useless behind their teams. A retiring force, therefore, of whatever size--from a company to an army--can only safely effect its retirement by detaching one fraction from its total which shall hold up the pursuit for a time while the main body gets away. When this detached fraction is wearied or imperilled, another fraction relieves it, taking up the same task in its turn; the first fraction, which had hitherto been checking the pursuit, falls back rapidly on to the main body, under cover of the new rearguard's fire as it turns to face the enemy. And the process is kept up, first one, then another portion of the whole force being devoted to it, until the retirement of the whole body has been successfully effected, and it is well ahead of its pursuers and secure. [Illustration: Sketch 47.]