|La Monoeuver sur les derrieres schematic|
La manoeuvre sur les derrieres was employed no less than thirty times between 1796 and 1815 and was designed to crush a single enemy army which had strayed out of close supporting distance of its allies or supporting forces. Its aim was to achieve a favorable battle situation on Napoleon's own terms. The Emperor, while he was quite prepared "to break eggs to make omlettes," as von Clauswitz puts it, was always eager to gain total victory for a minimum expenditure of manpower and effort. Consequently he disliked having to force a full-scale, fully arrayed frontal battle -- that is to say, marching directly against the enemy to fight him on ground of his (the adversary's) choosing, for such battles were inevitably expensive and rarely conclusive (Borodino in 1812 is a case in point). Instead, whenever possible, after pinning the foe frontally by a feint attack, he marched his main army by the quickest possible "safe" route, hidden by the cavalry screen and natural obstacles, to plce himself on the rear or flank of his opponent. Once this move had been successfully achieved, he occupied a natural barrier or "strategical curtain" (usually a river line o mountain range), ordered the blocking of all crossings, and thus isolated his intended victim from his rear depots and reduced his chances of reinforcement. Thereafter, Napoleon advanced relentlessly toward the foe's army, offering him only two alternatives -- to fight for survival on ground not of his own choosing, or to surrender.
The advantages afforded by such a strategy are obvious. The enemy army would be both taken by surprise and almost certainly demoralized by the sudden apparition of the enemy army in its rear, cutting its communications. The opposing general could attempt one of three things to try and remedy the situation; if he was bold enough, he could continue his advance against the "pinning" force; or, second, he could try to place himself across the main French lines of communication -- which would necessarily be extensive; or, third, h could order an immediate retreat toward the main French army in the hope of forcing a way through to reopn his communications -- in other words, accepting a battle.
~ The Campaigns of Napoleon, D. Chandler, p. 163