Official Records of the Rebellion

No.2. Reports of Brig. Gen. John G. Barnard, U. S. Army, Chief Engineer of operations from May 23, 1861, to August 15, 1862.

[p.107: SPLIT 2: COMPARES TO lines of Torres Vedras]

I refrain from making here an exact enumeration or a minute description of the works. A report to the Chief Engineer, U. S. Army, made by me December 10, 1861, in compliance with a resolution of the House of Representatives (a copy of which was furnished to General McClellan), will furnish all such details. They should not be made public. I incorporate in this report the following extract:

The aggregate perimeter of all the works is about 15,500 yards, or nearly 9 miles (including the stockaded gorges, which, however, form a small proportion of the whole), requiring, computed according to the rule adopted for the lines of Torres Vedras, 22,674 men (about) for garrison.

The number of guns (most of which are actually mounted) is about 480, requiring about 7,200 men to furnish three reliefs of gunners. The permanent garrisons need consist of only these gunners, and even in case of attack it will seldom be necessary to keep full garrisons in all the works.

The total garrisons for all the works (152 in number) of Torres Vedras amounted to 34,125 men, and as the total perimeters are nearly proportional to the total garrisons, it appears that the lines about Washington involve a magnitude of works of about two-thirds of that in the three lines of Torres Vedras.

The works themselves, fewer in number, are generally much larger than those of Torres Vedras, and involve, I believe, when the amount of bomb-proof shelter is considered, more labor per yard of perimeter, but the latter lines involved a far greater amount of auxiliary work, such a the scarping of mountain slopes, palisading, abatis, roads, &e., than we have had occasion to make.

The lines of Torres Vedras were armed with 534 pieces of ordnance (12, 9 or 6 pounders with a few field howitzers); ours with 480 pieces, of which the greater number are 32-pounders on barbette carriages, the rest being 24-pounders on the same carriages, 24-pounder siege guns, 10, 20, and 30 pounder rifled guns (Parrott), with a few field pieces and howitzers.

As to number of guns, therefore, our armament approaches to equality with the famous lines mentioned. In weight of metal it more than doubles it.

The above applies to our works as now nearly completed, and has no reference to the additional works I have elsewhere mentioned as hereafter necessary. (Very considerable changes in works, armament, &c., have been made since the above account was written, which applies to their state when the Army of the Potomac left Washington, March, 1862.)

* * * * * *

It remains with me to express my sense of the zeal and efficiency with which the officers of engineers serving with me since last April have discharged their duties.

The theory of these defenses is that upon which the works of Torres Vedras were based, the only one admitted at the present day for defending extensive lines. It is to occupy the commanding points within cannon range of each other by field forts, the fire of which shall sweep all approaches. These forts furnish the secure emplacements of artillery. They also afford cover to bodies of infantry. The works may be connected by lines of light parapets, or the ground (where practicable) may be so obstructed that the enemy’s troops cannotpenetrate the [p.108] in-terval without being exposed for considerable time to the destructive effects of the artillery or musketry fire of the forts.

With such a system established, the defense against a powerful attack requires that all the forts shall be garrisoned; that a certain amount of infantry, cavalry, and movable artillery be distributed along the lines sufficient to hold them until reserves can be brought to their support; and, finally, it requires a movable force held as a reserve which may be shifted from point to point to meet the enemy’s effort wherever it may be made, and where, aided by the works, they can repel superior numbers.

It is evident that without fortifications a place cannot be considered secure unless held by considerably greater numbers than the enemy can bring to assail it. No less an authority than Napoleon says that, aided by fortifications, 50,000 men and 3,000 artillerymen can defend a capital against 300,000 men, and he asserts the necessity of fortifying all national capitals.

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