The difficulty of moving provisions, baggage, &c., in a retreat, is always very great, and the very best generals have frequently failed on this point. Indeed, the best concerted measures will sometimes fail, amid the confusion and disorder consequent upon a retreat with an able and active enemy in pursuit. In such a case, the loss of the provision-trains in a sterile or unfriendly country may lead to the most terrible disasters. We will allude to two examples of this kind: the retreat of the English from Spain in 1809, and that of the French from Russia in 1812. When Sir John Moore saw that a retreat had become necessary to save his army from entire destruction, he directed all the baggage and stores to be taken to the rear, and every possible arrangement to be made for their preservation and for the regular supplies of the army. But the want of discipline in his troops, and more especially the want of a proper engineer organization to prepare the requisite means for facilitating his own marches, and impeding the enemy's pursuit, prevented his plans from being fully carried into execution. Much suffering and great losses were consequently inflicted upon his troops; a large portion of his baggage and military stores was captured, and even the treasure of his army, amounting to some 200,000 dollars, was abandoned through the ignorance and carelessness of the escorting officer. In Napoleon's march into Russia, his plans had been so admirably combined, that from Mentz to Moscow not a single estafette or convoy, it is said, was carried off in this campaign; nor was there a day passed without his receiving intelligence from France. When the retreat was begun, (after the burning of Moscow,) he had six lines of magazines in his rear; the 1st, at Smolensk, ten days' march from Moscow; those of the 2d line at Minsk and Wilna, eight marches from Smolensk; those of the 3d line at Kowno, Grodno, and Bialystok; those of the 4th line at Elbing, Marienwerder, Thorn, Plock, Modlin, and Warsaw; those of the 5th line at Dantzic, Bamberg, and Posen; those of the 6th line at Stettin, Custrin, and Glogau. When the army left Moscow it carried with it provisions sufficient for twenty days, and an abundance of ammunition, each piece of artillery being supplied with three hundred and fifty rounds; but the premature cold weather destroyed thirty thousand horses in less than three days, thus leaving the trains without the means of transportation or suitable escorts for their protection: the horrible sufferings of the returning army now surpassed all description. The officer selected to escort convoys should be a man of great prudence, activity, and energy, for frequently very much depends upon the safe and timely arrival of the provisions and military stores which he may have in charge.