To avoid this danger it is necessary to give such a direction to the line of operations that our army shall preserve its communications and be able to reach its base.
Thus, if Napoleon, in 1800, after crossing the Alps, had marched by Turin on Alexandria and received battle at Marengo, without having first secured Lombardy and the left of the Po, his own line of retreat would have been completely cut off by Melas; whereas, by the direction which he gave to his line of operations he had, in case of reverse, every means for reaching either the Var or the Valois.

(Fig.

6.) Again, in 1806, if he had marched directly from Gera to Leipsic, he would have been cut off from his base on the Rhine; whereas, by turning from Gera towards Weimar, he not only cut off the Prussians from the Elbe, but at the same time secured to himself the roads of Saalfield, Schleitz, and Hoff, thus rendering perfectly safe his communications in his rear.
(Fig.

7.) We have said that the configuration of the ground and the position of the hostile forces may _sometimes_ render it advisable to direct our line of operations against the extremity of the enemy's line of defence; but, _as a general rule_ a central direction will lead to more important results.

This severs the enemy's means of resistance, and enables the assailant to strike, with the mass of his force, upon the dissevered and partially paralyzed members of the hostile body.