two armies on the march gives
rise to one of the most imposing scenes in war.

In the greater number of battles, one party awaits his enemy in a
position chosen in advance, which is attacked after a reconnoissance as
close and accurate as possible. It often happens, however,--especially
as war is now carried on,--that two armies approach each other, each
intending to make an unexpected attack upon the other. A collision
ensues unexpected by both armies, since each finds the other where it
does not anticipate a meeting. One army may also be attacked by another
which has prepared a surprise for it,--as happened to the French at
Rossbach.

A great occasion of this kind calls into play all the genius of a
skillful general and of the warrior able to control events. It is always
possible to gain a battle with brave troops, even where the commander
may not have great capacity; but victories like those of Lutzen,
Luzzara, Eylau, Abensberg, can only be gained by a brilliant genius
endowed with great coolness and using the wisest combinations.

There is so much chance in these accidental battles that it is by no
means easy to lay down precise rules concerning them; but these are the
very cases in which it is necessary to keep clearly before the mind the
fundamental principles of the art and the different methods of applying
them, in order to a proper arrangement of maneuvers that must be decided
upon at the instant and in the midst of the crash of resounding arms.

Two armies marching, as they formerly did, with all their camp-equipage,
and meeting unexpectedly, could do nothing better at first than cause
their advanced guard to deploy to the right or left of the roads they
are traversing. In each army the forces should at the same time be
concentrated so that they may be thrown in a proper direction
considering the object of the march. A grave error would be committed in
deploying the whole army behind the advanced guard; because, even if the
deployment were accomplished, the result would be nothing more than a
badly-arranged parallel order, and if the enemy pressed the advanced
guard with considerable vigor the consequence might be the rout of the
troops which were forming. (See the account of the battle of Rossbach,
Treatise on Grand Operations.)

In the modern system, when armies are more easily moved, marching upon
several roads, and divided into masses which may act independently,
these routs are not so much to be fear