rward movement by echelon and preserving all the
advantages of concentration of fire. These advantages vanish if the
enemy, instead of foolishly throwing himself upon the retired center, is
content to watch it from a distance and makes his greatest effort upon
one wing. Essling, in 1809, is an example of the advantageous use of a
concave line; but it must not be inferred that Napoleon committed an
error in attacking the center; for an army fighting with the Danube
behind it and with no way of moving without uncovering its bridges of
communication, must not be judged as if it had been free to maneuver at
pleasure.

[Illustration: Fig. 13.]

The convex order with the center salient (Fig. 13) answers for an
engagement immediately upon the passage of a river when the wings must
be retired and rested on the river to cover the bridges; also when a
defensive battle is to be fought with a river in rear, which is to be
passed and the defile covered, as at Leipsic; and, finally, it may
become a natural formation to resist an enemy forming a concave line. If
an enemy directs his efforts against the center or against a single
wing, this order might cause the ruin of the whole army.[26]

The French tried it at Fleurus in 1794, and were successful, because
the Prince of Coburg, in place of making a strong attack upon the center
or upon a single extremity, divided his attack upon five or six
diverging lines, and particularly upon both wings at once. Nearly the
same convex order was adopted at Essling, and during the second and
third days of the famous battle of Leipsic. On the last occasion it had
just the result that might have been expected.

[Illustration: Fig. 14
A
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT

_____ _____
_____ _____
_____ _____
_____ B _____
_______
]
The order by echelon upon the two wings Fig. 14 is of the same nature as
the perpendicular order, (Fig. 11,) being, however, better than that,
because, the echelons being nearest each other in the direction where
the reserve would be placed, the enemy would be less able, both as
regards room and time, to throw himself into the interval of the center
and make at that point a threatening counter-attack.

[Illustration: Fig. 15
A
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT

___|___
___|