he disastrous events which
may attend a rapid retreat across a large river.

_Tetes de ponts_ are doubly advantageous when they are as it were
_keeps_ for a large intrenched camp, and will be triply so if they also
cover the bank opposite to the location of the camp, since then they
will mutually support each other. It is needless to state that these
works are particularly important in an enemy's country and upon all
fronts where there are no permanent works. It may be observed that the
principal difference between the system of intrenched camps and that of
_tetes de ponts_ is that the best intrenched camps are composed of
detached and closed works, while _tetes de ponts_ usually consist of
contiguous works not closed. An intrenched line to admit of defense must
be occupied in force throughout its whole extent, which would generally
require a large army; if, on the contrary, the intrenchments are
detached closed works, a comparatively small force can defend them.

The attack and defense of these works will be discussed in a subsequent
part of this volume.

ARTICLE XXVIII.

Strategic Operations in Mountains.

A mountainous country presents itself, in the combinations of war, under
four different aspects. It may be the whole theater of the war, or it
may be but a zone; it may be mountainous throughout its whole extent, or
there may be a line of mountains, upon emerging from which the army may
debouch into large and rich plains.

If Switzerland, the Tyrol, the Noric provinces, some parts of Turkey and
Hungary, Catalonia and Portugal, be excepted, in the European countries
the mountains are in single ranges. In these cases there is but a
difficult defile to cross,--a temporary obstacle, which, once overcome,
is an advantage rather than an objection. In fact, the range once
crossed and the war carried into the plains, the chain of mountains may
be regarded as an eventual base, upon which the army may fall back and
find a temporary refuge. The only essential precaution to be observed
is, not to allow the enemy to anticipate the army on this line of
retreat. The part of the Alps between France and Italy, and the
Pyrenees, (which are not so high, though equally broad,) are of this
nature. The mountains of Bohemia and of the Black Forest, and the
Vosges, belong to this class. In Catalonia the mountains cover the whole
country as far as the Ebro: if the war were limited to this province,
the combinations would not