CHAPTER III.
FORTIFICATIONS.
_Fortifications, or engineering_, may be considered with reference to the defence of states and the grand operation of armies; or with reference to the details of the construction, and attack, and defence of forts, and the influence of field-works on the tactical manoeuvres of armies.

It is proposed to speak here only of its general character, as a branch of the military art, without entering into any professional discussion of details.
The connection of fortification and strategy may be considered under two distinct heads: 1st, the choice of sites for constructing fortresses for defence; 2d, their influence in offensive operations, and the determination of the question whether they can be passed with safety, or whether the attacking force will be under the necessity of besieging them.
The centre and extremities of _a base of operations_ should always be secured either by natural or artificial obstacles.

This base is generally chosen so that fortifications will be necessary for strengthening only a part of the line.

But if a frontier, like the side of France towards Belgium, be destitute of natural obstacles, the artificial means of defence must be proportionally increased.

Great care should be taken that permanent fortifications be made only on such places as may favor military operations.