The letter A in this and other figures of the twelve orders indicates the defensive army, and B the offensive. The armies are represented each in a single line, in order not to complicate the figures too much; but it should be observed that every order of battle ought to be in two lines, whether the troops are deployed in columns of attack, in squares, or checkerwise.
An attack upon the two extremities might succeed also in some cases, either when the force was strong enough to try it, or the enemy was unable to weaken his center to support the wings. As a rule, a false attack to engage the center, and a strong attack against one extremity, would be the best method to use against such a line.
The great reserves must, of course, be also engaged when it is necessary; but it is always a good plan to keep back, as a final reserve, two or three battalions and five or six squadrons. Moreau decided the battle of Engen with four companies of infantry; and what Kellermann's cavalry accomplished at Marengo is known to every reader of history.