s,
Suchet in Catalonia and Massena in Portugal each had a strategic front,
while the front of some other corps of the army was not clearly defined.

LINES OF DEFENSE.

Lines of defense are classified as strategical and tactical. Strategical
lines of defense are subdivided into two classes: 1. Permanent lines of
defense, which are a part of the defensive system of a state, such as
the line of a fortified frontier; 2. Eventual lines of defense, which
relate only to the temporary position of an army.

The frontier is a permanent line of defense when it presents a
well-connected system of obstacles, natural and artificial, such as
ranges of mountains, broad rivers, and fortresses. Thus, the range of
the Alps between France and Piedmont is a line of defense, since the
practicable passes are guarded by forts which would prove great
obstacles in the way of an army, and since the outlets of the gorges in
the valleys of Piedmont are protected by large fortresses. The Rhine,
the Oder, and the Elbe may also be considered as permanent lines of
defense, on account of the important forts found upon them.

Every river of any considerable width, every range of mountains, and
every defile, having their weak points covered by temporary
fortifications, may be regarded as _eventual lines of defense_, both
strategic and tactical, since they may arrest for some time the progress
of the enemy, or may compel him to deviate to the right or left in
search of a weaker point,--in which case the advantage is evidently
strategic. If the enemy attack in front, the lines present an evident
tactical advantage, since it is always more difficult to drive an army
from its position behind a river, or from a point naturally and
artificially strong, than to attack it on an open plain. On the other
hand, this advantage must not be considered unqualified, lest we should
fall into the system of positions which has been the ruin of so many
armies; for, whatever may be the facilities of a position for defense,
it is quite certain that the party which remains in it passive and
receiving all the attacks of his adversary will finally yield.[9] In
addition to this, since a position naturally very strong[10] is
difficult of access it will be as difficult of egress, the enemy may be
able with an inferior force to confine the army by guarding all the
outlets. This happened to the Saxons in the camp of Pirna, and to
Wurmser in Mantua.

STRATEGIC POSITIONS.

T