mmunications either intersect or meet, and the centre of an arc which
is occupied by the enemy, are strategic points; but tactics would reject
a position equally accessible on all sides, especially with its flanks
exposed to attack. Sempronius at Trebbia and Varro at Cannae, so placed
their armies that the Carthagenians attacked them, at the same time, in
front, on the flanks, and in rear; the Roman consuls were defeated: but
the central strategic position of Napoleon at Rivoli was eminently
successful. At the battle of Austerlitz the allies had projected a
_strategic_ movement to their left, in order to cut off Napoleon's right
from Vienna; Weyrother afterwards changed his plans, and executed a
corresponding _tactical_ movement. By the former there had been some
chance of success, but the latter exposed him to inevitable destruction.
The little fort of Koenigsten, from its advantageous position, was more
useful to the French, in 1813, than the vast works of Dresden. The
little fort of Bard, with its handful of men, was near defeating the
operations of Napoleon in 1800, by holding in check his entire army;
whereas, on the other hand, the ill-advised lines of Ticino, in 1706,
caused an army of 78,000 French to be defeated by only 40,000 men under
Prince Eugene of Savoy.

War, as has already been said, may be either offensive or defensive. If
the attacking army be directed against an entire state, it becomes a war
of _invasion_. If only a province, or a military position, or an army,
be attacked, it is simply regarded as taking the _initiative_ in
offensive movements.

_Offensive_ war is ordinarily most advantageous in its moral and
political influence. It is waged on a foreign soil, and therefore spares
the country of the attacking force; it augments its own resources at the
same time that it diminishes those of the enemy; it adds to the moral
courage of its own army, while it disheartens its opponents. A war of
invasion may, however, have also its disadvantages. Its lines of
operation may become too _deep_, which is always hazardous in an enemy's
country. All the natural and artificial obstacles, such as mountains,
rivers, defiles, fortifications, &c., are favorable for defence, but
difficult to be overcome by the invader. The local authorities and
inhabitants oppose, instead of facilitating his operations; and if
patriotism animate the defensive army to fight for the independence of
its threatened country, the war may