Tactically the greater concentration guarantees tactical success, and strategically it allows greater freedom of movement and changes of direction to meet altered conditions; but one must never lose sight of the technical drawbacks such closer concentration entails.
The zone of reconnaissance is naturally always of less breadth than with divided columns; hence the possibility of screening the march of troops in the rear is diminished, the risk of being turned is increased, and the possibility of delivering a stroke in the air is not inconsiderable.
If the enemy wishes to evade us, we have scarcely any means of holding him until our main force can arrive; and finally, this condition of close concentration by no means guarantees always and everywhere either superior readiness for action or a more favourable deployment. Cases can arise in which strategic dispersion will prepare the way for tactical encounter even better than the concentrated advance; and this is particularly so when, to attain the object of our mission, a wide turning movement is necessary, for this will generally be best brought about by previous strategic dispositions; whilst the deployment of a mass from a defile or its retreat may be entirely prevented if attempted in a single column.
Hence every principle has its limitations, and circumstances will always arise which defy all stereotyped formations. Thus, even for 'screening' and 'security' cases can arise under which concentration is justified, even where the nature of the ground does not imperatively dictate it, as when, for instance, the insufficiency of one's own force excludes any distribution in breadth, and compels one to combine all efforts for the defence of decisive points. And it is precisely on the defensive that it may be of advantage to deal a blow with the concentrated strength. Equally on the strategic offensive, dispersion may be necessary, as when the enemy retreats eccentrically; or if it is necessary to occupy districts of considerable size to break down the resistance of the hostile population, or to interrupt railway communication over a considerable area.
Finally, all principles fall to the ground where the enemy's Cavalry is finally beaten out of the field, or by a succession of mistakes he gives openings which we can seize with advantage. Thus our conduct always remains dependent on the topographical nature of the country, on our own purpose and the opposition of the enemy, and only one law governs all cases--namely, expediency. The greater art of leading will naturally be required when the necessity arises to operate with more or less widely-separated columns. In all such cases everything depends on the endurance of one's troops. The principal difficulty in the way of execution lies in harmonizing and maintaining the movements of the separate detachments.