Quicker transport was, however, only one consideration. There was the further important detail that the movement of troops by rail would bring them to their point of concentration, not only sooner, but in more complete numbers, than if they had to endure the fatigues of prolonged marches by road.
According to German authorities, the falling-out of infantry and cavalry when marching along good roads under conditions of well-maintained discipline and adequate food supplies averages three per cent. in cool and dry weather, and six per cent. in hot or wet weather; while in unfavourable conditions as regards roads, weather and supplies, the diminution may be enormous. When, in the autumn of 1799, Suvóroff made his famous march over the St. Gothard, he lost, in eleven days, no fewer than 10,000 men owing to the hardships of the journey. In his invasion of Russia, in 1812, Napoleon's losses in men who succumbed to the fatigues and trials they experienced on the road were out of all proportion to the casualties due to actual fighting. It was, too, a saying of Blücher's that "he feared night marches worse than the enemy."
An English authority, Lieut.-Col. R. Home, C.B., R.E., wrote in a paper on "The Organisation of the Communications, including Railways," published in Vol XIX. of the Journal of the Royal United Service Institution (1875):—
If an army of moderate size, say 50,000 men, simply marches one hundred miles without firing one shot or seeing an enemy the number of sick to be got rid of is very great.
Experience has shown that in a good climate, with abundant food, easy marches, and fair weather, the waste from ordinary causes in a ten days' march of such a force would be between 2,000 and 2,500 men, while the number of galled, footsore or worn-out horses would also be very large. A few wet days or a sharp engagement would raise the number of both very considerably. An inefficient man or horse at the front is a positive disadvantage.
Another equally important detail relates to the provision of supplies for the troops and animals thus transported by rail both more quickly and with less fatigue.
In all ages the feeding of his troops in an enemy's country has been one of the gravest problems a military commander has had to solve; and though, in some instances, vast armies have succeeded in drawing sufficient support from the land they have invaded, there have been others in which an army intending to "live upon the country" has failed to get the food it needed, and has had its numbers depleted to the extent of thousands as the result of sheer starvation. This was the experience of Darius, King of Persia, who, in 513 B.C., crossed the Bosporus, on a bridge of boats, with an army of 700,000, followed the retreating Scythians, and lost 80,000 of his men in wild steppes where no means existed for feeding them. When, also, Alexander the Great was withdrawing from India, in 325 B.C., two-thirds of his force died on the desert plains of Beluchistan from thirst or hunger. Lack of the supplies from which he found himself entirely cut off was, again, a main cause of the disaster that overtook Napoleon in his Russian campaign. Even fertile or comparatively fertile lands, satisfying the needs of their inhabitants in time of peace, may fail to afford provisions for an invading army, either because of the great number of the latter or because the retreating population have destroyed the food supplies they could not take with them into the interior whether for their own sustenance or with a view to starving the invaders.
Should the invading army succeed in "living on the country," the effect of leaving the troops to their own resources, in the way of collecting food, may still be not only subversive of discipline but of strategic disadvantage through their being scattered on marauding expeditions at a time when, possibly, it would be preferable to keep them concentrated.
General Friron, chief of the staff of Marshal Masséna, wrote concerning Napoleon's campaign in Portugal:—
The day the soldier became convinced that, for the future, he would have to depend on himself, discipline disappeared from the ranks of the army. The officer became powerless in the presence of want; he was no longer disposed to reprimand the soldier who brought him the nourishment essential to his existence, and who shared with him, in brotherly goodwill, a prey which may have cost him incalculable dangers and fatigues.
The extent to which a combination of physical fatigue and shortness of supplies in an inhospitable country may interfere with the efficiency of an army is well shown by Thiers ("Histoire du Consulat et de l'Empire") in regard to the conditions at the very outset of Napoleon's Russian campaign. The French troops arriving on the Niemen—at which point they were merely on the frontiers of Russia—were already overcome by the long marches they had made. They had no bread, no salt, and no spirits; their craving for food could no longer be satisfied by meat without salt and meal mixed with water. The horses, too, were out of condition for want of proper food. Behind the army a great number of soldiers dropped out of the ranks and had lost their way, while the few people they met in a scantily-populated district could speak nothing but Polish, which the wearied and famished men were unable to understand. Yet, under the conditions of former days, it was by troops thus exhausted by marches of hundreds of miles, done on, possibly, a starvation diet, that battles involving the severest strain on human energy were fought.