Respecting the length of a march and the time it requires, it is natural for us to depend on the general results of experience.
For our modern armies it has long been settled that a march of three miles should be the usual day’s work which, on long distances, may be set down as an average distance of two miles per day, allowing for the necessary rest days, to make such repairs of all kinds as may be required.
Such a march in a level country, and on tolerable roads will occupy a division of 8,000 men from eight to ten hours; in a hilly country from ten to twelve hours. If several divisions are united in one column, the march will occupy a couple of hours longer, without taking into account the intervals which must elapse between the departure of the first and succeeding divisions.
We see, therefore, that the day is pretty well occupied with such a march; that the fatigue endured by a soldier loaded with his pack for ten or twelve hours is not to be judged of by that of an ordinary journey of three miles on foot which a person, on tolerable roads, might easily get over in five hours.
The longest marches to be found in exceptional instances are of five, or at most six miles a day; for a continuance four.
A march of five miles requires a halt for several hours; and a division of 8,000 men will not do it, even on a good road, in less than sixteen hours. If the march is one of six miles, and that there are several divisions in the column, we may reckon upon at least twenty hours.
We here mean the march of a number of whole divisions at once, from one camp to another, for that is the usual form of marches made on a theatre of war. When several divisions are to march in one column, the first division to move is assembled and marched off earlier than the rest, and therefore arrives at its camping ground so much the sooner. At the same time this difference can still never amount to the whole time, which corresponds to the depth of a division on the line of march, and which is so well expressed in French, as the time it requires for its découlement (running down). The soldier is, therefore, saved very little fatigue in this way, and every march is very much lengthened in duration in proportion as the number of troops to be moved increases. To assemble and march off the different brigades of a division, in like manner at different times, is seldom practicable, and for that reason we have taken the division itself as the unit.
In long distances, when troops march from one cantonment into another, and go over the road in small bodies, and without points of assembly, the distance they go over daily may certainly be increased, and in point of fact it is so, from the necessary detours in getting to quarters.
But those marches, on which troops have to assemble daily in divisions, or perhaps in corps, and have an additional move to get into quarters, take up the most time, and are only advisable in rich countries, and where the masses of troops are not too large, as in such cases the greater facilility of subsistence and the advantage of the shelter which the troops obtain compensate sufficiently for the fatigue of a longer march. The Prussian army undoubtedly pursued a wrong system in their retreat in 1806 in taking up quarters for the troops every night on account of subsistence. They could have procured subsistence in bivouacs, and the army would not have been obliged to spend fourteen days in getting over fifty miles of ground, which, after all, they only accomplished by extreme efforts.
If a bad road or a hilly country has to be marched over, all these calculations as to time and distance undergo such modifications that it is difficult to estimate, with any certainty, in any particular case, the time required for a march; much less, then, can any general theory be established. All that theory can do is to direct attention to the liability to error with which we are here beset. To avoid it the most careful calculation is necessary, and a large margin for unforeseen delays. The influence of weather and condition of the troops also come into consideration.
Since the doing away with tents and the introduction of the system of subsisting troops by compulsory demands for provisions on the spot, the baggage of an army has been very sensibly diminished, and as a natural and most important consequence we look first for an acceleration in the movements of an army, and, therefore, of course, an increase in the length of the day’s march. This, however, is only realized under certain circumstances.
Marches within the theatre of war have been very little accelerated by this means, for it is well known that for many years whenever the object required marches of unusual length it has always been the practice to leave the baggage behind or send it on beforehand, and, generally, to keep it separate from the troops during the continuance of such movements, and it had in general no influence on the movement, because as soon as it was out of the way, and ceased to be a direct impediment, no further trouble was taken about it, whatever damage it might suffer in that way. Marches, therefore, took place in the Seven Years’ War, which even now cannot be surpassed; as an instance we cite Lascy’s march in 1760, when he had to support the diversion of the Russians on Berlin, on that occasion he got over the road from Schweidnitz to Berlin through Lusatia, a distance of 225 miles, in ten days, averaging, therefore, twenty-two miles a day, which, for a Corps of 15,000, would be an extraordinary march even in these days.
On the other hand, through the new method of supplying troops the movements of armies have acquired a new retarding principle. If troops have partly to procure supplies for themselves, which often happens, then they require more time for the service of supply than would be necessary merely to receive rations from provision wagons. Besides this, on marches of considerable duration troops cannot be encamped in such large numbers at any one point; the divisions must be separated from one another, in order the more easily to manage for them. Lastly, it almost always happens that it is necessary to place part of the army, particularly the cavalry, in quarters. All this occasions on the whole a sensible delay. We find, therefore, that Buonaparte in pursuit of the Prussians in 1806, with a view to cut off their retreat, and Blücher in 1815, in pursuit of the French, with a like object, only accomplished thirty miles in ten days, a rate which Frederick the Great was able to attain in his marches from Saxony to Silesia and back, notwithstanding all the train that he had to carry with him.
At the same time the mobility and handiness, if we may use such an expression, of the parts of an army, both great and small, on the theatre of war have very perceptibly gained by the diminution of baggage. Partly, inasmuch as while the number of cavalry and guns is the same, there are fewer horses, and therefore, there is less forage required; partly, inasmuch as we are no longer so much tied to any one position, because we have not to be for ever looking after a long train of baggage dragging after us.
Marches such as that, which, after raising the siege of Olmütz, 1758, Frederick the Great made with 4,000 carriages, the escort of which employed half his army broken up into single battalions and companies, could not be effected now in presence of even the most timid adversary.
On long marches, as from the Tagus to the Niemen, that lightening of the army is more sensibly felt, for although the usual measure of the day’s march remains the same on account of the carriages still remaining, yet, in cases of great urgency, we can exceed that usual measure at a less sacrifice.
Generally the diminution of baggage tends more to a saving of power than to the acceleration of movement.
