learn any thing about them. Spies may, however, be very useful when the
hostile army is commanded by a great captain or a great sovereign who
always moves with the mass of his troops or with the reserves. Such, for
example, were the Emperors Alexander and Napoleon. If it was known when
they moved and what route they followed, it was not difficult to
conclude what project was in view, and the details of the movements of
smaller bodies needed not to be attended to particularly.

A skillful general may supply the defects of the other methods by making
reasonable and well-founded hypotheses. I can with great satisfaction
say that this means hardly ever failed me. Though fortune never placed
me at the head of an army, I have been chief of staff to nearly a
hundred thousand men, and have been many times called into the councils
of the greatest sovereigns of the day, when the question under
consideration was the proper direction to give to the combined armies of
Europe; and I was never more than two or three times mistaken in my
hypotheses and in my manner of solving the difficulties they offered. As
I have said before, I have constantly noticed that, as an army can
operate only upon the center or one extremity of its front of
operations, there are seldom more than three or four suppositions that
can possibly be made. A mind fully convinced of these truths and
conversant with the principles of war will always be able to form a plan
which will provide in advance for the probable contingencies of the
future. I will cite a few examples which have come under my own
observation.

In 1806, when people in France were still uncertain as to the war with
Prussia, I wrote a memoir upon the probabilities of the war and the
operations which would take place.

I made the three following hypotheses:--1st. The Prussians will await
Napoleon's attack behind the Elbe, and will fight on the defensive as
far as the Oder, in expectation of aid from Russia and Austria; 2d. Or
they will advance upon the Saale, resting their left upon the frontier
of Bohemia and defending the passes of the mountains of Franconia; 3d.
Or else, expecting the French by the great Mayence road, they will
advance imprudently to Erfurt.

I do not believe any other suppositions could be made, unless the
Prussians were thought to be so foolish as to divide their forces,
already inferior to the French, upon the two directions of Wesel and
Mayence,--a useless mistake, since