arengo without having previously
protected himself on the side of Lombardy and of the left bank of the
Po, he would have been more thoroughly cut off from his line of retreat
than Melas from his; but, having in his possession the secondary points
of Casale and Pavia on the side of the Saint-Bernard, and Savona and
Tenda toward the Apennines, in case of reverse he had every means of
regaining the Var or the Valais.

In 1806, if he had marched from Gera directly upon Leipsic, and had
there awaited the Prussian army returning from Weimar, he would have
been cut off from the Rhine as much as the Duke of Brunswick from the
Elbe, while by falling back to the west in the direction of Weimar he
placed his front before the three roads of Saalfeld, Schleiz, and Hof,
which thus became well-covered lines of communication. If the Prussians
had endeavored to cut him off from these lines by moving between Gera
and Baireuth, they would have opened to him his most natural line,--the
excellent road from Leipsic to Frankfort,--as well as the two roads
which lead from Saxony by Cassel to Coblentz, Cologne, and even Wesel.

4. Two independent armies should not be formed upon the same frontier:
such an arrangement could be proper only in the case of large
coalitions, or where the forces at disposal are too numerous to act upon
the same zone of operations; and even in this case it would be better to
have all the forces under the same commander, who accompanies the
principal army.

5. As a consequence of the last-mentioned principle, with equal forces
on the same frontier, a single line of operations will be more
advantageous than a double one.

6. It may happen, however, that a double line will be necessary, either
from the topography of the seat of war, or because a double line has
been adopted by the enemy, and it will be necessary to oppose a part of
the army to each of his masses.

7. In this case, interior or central lines will be preferable to
exterior lines, since in the former case the fractions of the army can
be concentrated before those of the enemy, and may thus decide the fate
of the campaign.[16] Such an army may, by a well-combined strategic
plan, unite upon and overwhelm successively the fractions of the
adversary's forces. To be assured of success in these maneuvers, a body
of observation is left in front of the army to be held in check, with
instructions to avoid a serious engagement, but to delay the enemy as
much as