From these cases it may be deduced that the enemy must be held at a distance, and that a large target must not be presented to him. The first is obtained by providing the forts with high power heavy guns for grazing fire to oppose vigorously the large calibre guns em ploying high angle fire, the only class that up to-date has sufficient mobility for siege trains. And to avoid the destruction of the works the thickness of armor and concrete cannot be much further increased, but the field fortifica tion system must be used; that is, the elements must be disseminated and a close co-operation with the field army must be maintained, while the latter, resting on the works, must not inter fere in the zone of action of the garrison.
Colonel Marrullier the Italian engineers presents two propositions: one purely technical and the other tactical. He would have (a) a line of auxiliary defenses, held by infantry and small calibre artillery; (b) a line of isolated turrets, separated by 30 or 40 metres; (c) a line of protected storehouses, to supply these turrets, 50 metres to the rear; (d) a line of shelters for personnel and material, 150 to 200 metres from the turrets; (e) a network of com municating trenches for every purpose in rear and between the lines. This general plan con forms to what appears to be necessary for future fortification.
Other writers agree in general with these ideas. All insist on an intimate co-operation between garrisons of fortified' places and the field armies, so as to prepare for the latter an advantageous field of battle. On the defensive the problem is to secure protection against the transportable heavy artillery of the assailant. The idea that permanent fortification is a thing of the past is fallacious. On the contrary, the correct tactical employment of troops still re quires the support of fortified places; and a proper use of these points of support embar rasses the enemy and increases the power of one's own troops.
The fortress of Ossowiez is a classical ex ample that a modern extensive field fortifica tion, which offers no concentrated targets to the enemy, can absolutely neutralize the power and effect of the latest siege mortars and howitzers. The hopes placed in the strongest fortified place in the world, Antwerp, were blasted by the wonderful progress made in the science of ordnance construction. The greatest ordnance triumph was the Austrian 42-centi meter howitzer, firing an 850-kilogram pro jectile, maximum range 15 kilometers. It was employed for the first time in the forcing of the Dunajec.
Most modern armored turrets for inland barrier forts are made of armor from 25 to 35 centimeters in thickness. The surrounding concrete is from 2 to 2.5 meters in thickness. Nevertheless this mass was absolutely de molished by the large calibre mortars used by the Germans and Austrians. Considering the terrible effect of these modern heavy mor tars,. we must concede their overwhelming superiority over the most modern armored forts. They , reduced Fort Loncin to a 'confused mass of twisted steel and broken concrete. Fort Manonvillers, the most power ful individual work in the world, was reduced to ruins. At Loncin an armored cupola 250 millimeters in thickness was completely perfor ated. At Longwy a shell pierced not only the armored cover but also went through three floors of the casemates.
Coast Fortifications.— The defense of coast line involves the use of both naval and land forces and the objects for which coast fortifications are established are as follows: (1) For the protection of important harbors and the shipping lying therein; (2) to prevent the bombardment of the largest coast cities; (3) to afford safe refuge to the fleet when con fronted by a superior enemy; (4) to protect the naval bases established in distant seas along the routes of trade. The limitations of coast
fortifications are great and perhaps the most vulnerable element in most cases is the fire control system, the stations of which are not adequately concealed nor properly covered. Since accuracy of plotting requires that observ ing points be fixed, mobility is not applicable to these stations.
The service of security and information in coast defense, as in the field, implies collection of military information, its transmission and its correlation and use. In the future coast patrol will undoubtedly become one of the strongest arms of the service of security and information and this patrol or guard must, when organized, be thoroughly efficient in num bers, personnel and equipment. Its men must be well-disciplined soldiers, intelligent and keen, skilled as observers and trained in the use of the telegraph and all mechanical appliances. In addition to fire-control systems there must exist both within and without artillery districts the factor of coast defense, that includes lines of information, whether electrical or visual, by means of which artillery headquarters are kept in touch with the interior of the country and with centres of control, the factors and elements of the defense brought into co-ordination, fixed positions connected and the district bound into a whole under the control of one commander. In general, artillery lines of fire-control and of information are, in times of peace, permanent in type; but in war to permanent lines are added a network of temporary systems both flexible and extensive, in character resembling those of an army in campaign. The tem porary lines of artillery districts must include many aerial systems, and even the permanent communications cannot be electrical alone.
The war of to-day is one of position, the front of which resembles a vast factory con taining every class of machine, each machine and its operator having a definite task to per form. The front is formed of numerous lines of continuous trenches, redoubts, fortified towns and woods placed in state of defense, all connected with lines of communication; the whole forming an enormous system of earth works, which may extend in a direction perpen dicular to the front, for a great distance. This complex system of trenches is divided into three zones, the organization of which varies with their mission as zones of combat, defense works or of rest.
Bibliography.— Army Field Engineer School 'Notes on Field Fortification' ; Army War College, 'Report of National Coast De fense Board' (Washington, D. C., 1906); Clarke, G. S., 'Fortification' (New York); Farrow, 'Manual of Military Training) (New York 1918) ; Fiebeger, 'Permanent Fortifica tions' (United States Military Academy, West Point), and 'Field Fortifications' (New York 1913) ; Thuillier, 'Principles of Land Defense) (New York 1902) ; United States Engineer School, 'Lectures on Sea Coast Defense' (Washington Barracks, D. C.).