Fortifications of the future will differ curiously from those of the present. The latter, with their towering scarps, their massive _enceintes_, their "portentous ditches," will remain as monuments of a vicious system, except where, as in the cases of Vienna, Cologne, Sedan, etc., the dwellers in the cities they encircle shall procure their demolition for the sake of elbow-room, or until modern howitzer shells or missiles charged with high explosives shall pulverise their naked expanses of masonry. In the fortification of the future the defender will no longer be "enclosed in the toils imposed by the engineer" with the inevitable disabilities they entail, while the besieger enjoys the advantage of free mobility. Plevna has killed the castellated fortress. With free communications the full results attainable by fortress artillery intelligently used, will at length come to be realised. Unless in rare cases and for exceptional reasons towns will gradually cease to be fortified even by an encirclement of detached forts. Where the latter are availed of, practical experience will infallibly condemn the expensive and complex cupola-surmounted construction of which General Brialmont is the champion. "A work," trenchantly argues Major Sydenham Clarke, "designed on the principles of the Roman catacombs is suited only for the dead, in a literal or in a military sense. The vast system of subterranean chambers and passages is capable of entombing a brigade, but denies all necessary tactical freedom of action to a battalion."
The fortress of the future will probably be in the nature of an intrenched camp. The interior of the position will provide casemate accommodation for an army of considerable strength. Its defences will consist of a circle at intervals of about 2500 yards, of permanent redoubts which shall be invisible at moderate ranges for infantry and machine guns, the garrison of each redoubt to consist of a half battalion. Such a work was in 1886 constructed at Chatham in thirty-one working days, to hold a garrison of 200 men housed in casemates built in concrete, for less than £3000, and experiments proved that it would require a "prohibitory expenditure" of ammunition to cause it serious damage by artillery fire. The supporting defensive armament will consist of a powerful artillery rendered mobile by means of tram-roads, this defence supplemented by a field force carrying on outpost duties and manning field works guarding the intervals between the redoubts. Advanced defences and exterior obstacles of as formidable a character as possible will be the complement of what in effect will be an immensely elaborated Plevna, which, properly armed and fully organised, will "fulfil all the requirements of defence" while possessing important potentialities of offence.