Elements of Military Art and Science / Or, Course Of Instruction In Strategy, Fortification, Tactics Of Battles, &C.; Embracing The Duties Of Staff, Infantry, Cavalry, Artillery, And Engineers; Adapted To The Use Of Volunteers And Militia; Third Edition; With Critical Notes On The Mexican And Crimean Wars.

by H. W. Halleck

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 manœuvres 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. If otherwise, the troops detached from the active army for garrisoning them, will only tend to weaken this force without any corresponding advantages. In this way, fortifications may become actually injurious to defence. A number of the European fortresses which were built before the subject of strategy was properly understood, are now regarded as utterly useless, from their ill-advised positions.

Whether a fortress may be safely passed with merely blockading or observing it, depends very much upon the nature of the war, and the numbers and position of the defensive army. The allies, in 1814, invading France with a million of soldiers, assisted by the political diversion of factions and Bourbonists within the kingdom, and treason in the frontier fortresses, and even in the ranks of Napoleon's army, could conduct their military operations on a very different plan from that which would be adopted by either Austria, Prussia, Russia, England, Spain, Portugal, Holland, Italy, and the German powers, if singly waging war with the French. Napoleon sometimes detached a corps to observe a fortress which threatened his line of operations or of manœuvre; at others, he delayed his advance till the place could be reduced.

"An army," says Jomini, "may sometimes penetrate between places on an open frontier, to attack the enemy's forces in the field, taking care at the same time to observe these places; but no invading army can cross a great river, like the Danube, the Rhine, or the Elbe, without reducing at least one of the fortresses on that river, so as to secure a line of retreat; but being in possession of such a place, it can continue the offensive, while its matériel de siège successively reduces the other places."

In case the main army is obliged to remain and cover the besieging corps, it should take some central position, where it can command all the avenues of approach, and fall with vigor on the enemy, should he attempt to raise the siege. Napoleon's operations before Mantua, in 1796, offer the finest model for imitation.

The old system of intrenched camps and lines of contravallation is unsuited to the spirit of modern warfare. In ancient times, and more particularly in the middle ages, too much importance was attached to tactical positions, and not enough to strategic points and lines. This gave to fortifications a character that never properly belonged to them. From the middle ages down to the period of the French Revolution, wars were carried on mainly by the system of positions—one party confining their operations to the security of certain important places, while the other directed their whole attention to the siege and capture of these places. But Carnot and Napoleon changed this system, at the same time with the system of tactics, or rather, returned from it to the old and true system of strategic operations. Some men, looking merely at the fact that a change was made, but without examining the character of that change, have rushed headlong to the conclusion that fortified places are now utterly useless in war, military success depending entirely upon a good system of marches.

On this subject, General Jomini, the great military historian of the wars of the French Revolution, remarks that "we should depend entirely upon neither organized masses, nor upon material obstacles, whether natural or artificial. To follow exclusively either of these systems would be equally absurd. The true science of war consists in choosing a just medium between the two extremes. The wars of Napoleon demonstrated the great truth, that distance can protect no country from invasion, but that a state, to be secure, must have a good system of fortresses, and a good system of military reserves and military institutions."