Here we have a dodecagon. The forts of the outer zone are seven thousand yards apart, and the works, A, flank each other; a second zone of forts B commands the latter, if required, and the zone of action of these second works extends beyond the outer line of forts. Railways are required to connect the forts of each zone, and to put them in communication with the body of the place.
This extension of the fields of defence may, according to the nature of the ground, be divided into two zones with a central nucleus.
Fig. 83.
The interior zone would consist of permanent works, forming an enceinte de préservation; a line of forts at intervals sufficiently strengthened, in case of war, by field works.
The exterior zone would be fixed by occupying strategic points well chosen and considered beforehand, forming small camps protected by temporary works, and affording security to a numerous army, whose manœuvres the enemy could not espy.
The expenditure entailed by such a system of defence is unquestionably enormous. But as respects this question there is to all appearance an unwillingness to realize exactly the new state of things produced by artillery of long range.
The expenditure involved in the successive systems of defence from ancient times downwards has been a continually increasing one. The wall built round Paris by Philippe-Augustus, would not cost, the running yard, as much as that of Charles V.; the latter, again, must have been less expensive than the bastioned fronts of Louis XIII., and these again would be far from necessitating the outlay (i.e. estimated by the running yard, and reckoning detached forts) occasioned by the fortification of Paris under Louis Philippe. Similarly the mounting of four or five trebuchets, and the movable towers required for attacking a fortified place before fire artillery was employed, cost less than the manufacture of the artillery used at the siege of Turin in 1535. The latter again would be far less costly than the French and English artillery at the siege of Sebastopol. Whereas at the time when smooth-bore guns were used a place might be attacked with about sixty pieces, five times the quantity are needed now; since it is necessary to operate over a much more extensive area.
War is therefore a game which tends to become more and more costly, and especially siege warfare. Are we then to conclude that nations will become disgusted with warfare on account of the frightful expense it involves? This is not probable.