hampered by having to think of guarding its own bases against any attack likely to be made on them. If it had to do this its mobility would be lost. Naval bases, where ships can renew their fuel supplies, ammunition and stores of all sorts, and where they can repair damage, must be self-protected. Similarly, it is advantageous that certain commercial ports where a country receives large overseas traffic or where convoys are assembled for dispatch should be self-protected. Also, for strategical reasons certain harbours should be self-protected, where naval squadrons can lie at ease without jeopardizing their own safety or risk being caught like rats in a trap.
It is at ports of the above description that " coast defences " find their real use, and while, as stated above, such defences should be kept down to a minimum, they must be capable of doing their protective work effectively. The necessary scale of defence will vary with every nation; and, with the far-flung possessions of the British Empire and any country with overseas dependencies, the requirements will vary in every case. Many factors must be taken into account. The strength of the naval forces of the country in question, the strength of the naval forces of any possible enemy, the geographical position of the harbour in consideration with respect to the enemy and with respect to the main forces of the country to which it belongs all these points must be duly weighed in deciding on the scale of defences to be adopted, as well as the particular role which the harbour is intended to fill in the general fighting scheme.
Fixed defences may be said then to form a part of the scheme for utilizing the naval forces of a country, and it has been argued that these defences should be manned and controlled by the navy. In a few countries this is the practice, but in the majority it is not, and it would seem that the latter are right for the following reasons: the service and control of artillery afloat differs greatly from those of artillery in coast batteries; the use of artillery in such batteries is not very different from that in heavy batteries in land warfare. Therefore it would seem advisable to have coast batteries manned by land gunners and not by naval gunners. History has shown that the defences on the land side of a coast fortress are often the door by which an enemy seeks to enter, e.g. Sevastopol, Port Arthur, Tsingtao, and the Dardanelles in the World War. These land defences are very intimately connected with the fixed coast defences and also with the field land forces, which must form a part of the army and not of the navy. It is evident then that in the general scheme of defence of a defended port there must be some line of demarcation between naval and military control, involving the closest cooperation between the two wherever that line of demarcation is drawn. For these reasons alone it is argued that the proper line of demarcation should be that provided by nature, namely, the edge of the sea.
Adaptation of Coast Defences to Local Conditions. While coast defences will vary according to the scale on which they are based, they will also vary according to the local conditions of the place to which they are applied. These local conditions, apart from topographical considerations, fall into three main classes: (i) Defence of a harbour; (2) Defence of a channel; (3) Defence of a landing place. The greater number of cases will come within the first class.
(i) Defence of a Harbour. This may be a naval port, a commercial harbour or a strategical anchorage. The scale having been determined upon, the coast defences necessary will depend upon the different forms of attack to which the harbour may be exposed. Attack on the land side of the harbour by forces landed outside its rayon is omitted here, as it is a branch of land warfare and is dealt with elsewhere. It is sufficient to remark that in the past this has often been the most effective form of attack on a defended harbour. With this omission it may be said that the forms of attack are: (a) Bombardment; (6) Attempts to block narrow parts of the approach channel by sinking ships in the fairway and so sealing up the harbour; (c) Close attack by small torpedo craft on ships or dockgates, probably at night.
(a) Bombardment. This form of attack may be taken to in- clude not only bombardment of the object for which the har-
bour exists, such as a dockyard or anchorage, but also action, analogous to counter-battery in land warfare, agiinst the batteries protecting the harbour, as, in the event of bombard- ment these batteries naturally come into play. The positions of these batteries will largely depend upon the topography of the environs. There are two general types of harbours, namely, one with an approach channel, which may be either long or short and broad or narrow, or one where the coast-line is to all intents a straight line, the harbour being forme 1 by a slight indentation of the coast, or by artificial breakwaters.
Whenever possible the batteries should be pushed out as far as may be from the real object of defence. This has always been advisable, but in these days it is more than ever necessary. The fact must be faced that with the present long ranges a larger amount of ammunition will be necessary than previously to obtain hits on hostile vessels. This means expenditure of time, during which the vessels may be able to shell the area forming their point of attack and inflict damage.
It may be taken now that bombardment can take place from such distances as 50,000 or even 60,000 yd., and across inter- vening portions of land. If at all possible then the primary batteries should be pushed so far forward that they can keep ships beyond this distance, or be so far forward that they will bring an effective fire to bear on the ships at much less than ex- treme ranges, before the latter come within bombarding range.
This, however, is not always possible, and in the event of a straight coast-line the enemy will be practically equidistant from the batteries and from the object of their defence. This will undoubtedly be a great disadvantage to the batteries, and the number of guns will have to be greater than usual in order to occupy fully the attention of the hosti'e vessels.
In the past, when the range of artillery was shorter, it was sometimes necessary to construct forts in the sea itself in order to cover effectually the whole of a broad channel, e.g. Spithead, Kronstadt or the entrance to Tokyo Bay. Nowadays, however, this will practically never be necessary.
The experiences of the World War have shown that the number of guns required to defend a harbour is even less than it used to be. Enemy ships for one thing will be chary of approach- ing too close on account of mines, submarines and electrically- controlled torpedo craft, and the great superiority of modern land range-finders over ship range-finders will ensure greater accuracy on the part of the shore guns. These latter should be well dispersed and should be able at the same time to con- centrate their fire. Batteries with single guns would have their advantages, but there would always be the chance of a lucky hit from the sea putting the gun out of action and so silencing the fire from a portion of the defence. It is probable then that there will be always two guns in a battery, but they will be well separated by about 200 yd. or even more.
Form of Batteries. The form that batteries will take will undoubt- edly be influenced by the lessons of the war. Taking into consid- eration the long ranges in use and the dislike of ships to come close in, there are many advantages to be gained by making primary batteries into indirect-fire batteries, siting them where they will be unseen from the sea and controlling their fire at all times by some system of position-finding. The advantages so gained would be, increased protection from hostile fire, much greater latitude in the choice of sites, a great simplification in design due to the pro- tection the battery gains from its position and probably easier com- munications up to the battery. The disadvantages are, loss of range, a certain area of dead water in the foreground of the bat- tery, and the impossibility of fighting the guns in the event of the means of control of fire breaking down. The loss of range would be unavoidable but the amount would be small. The area of dead water would depend upon the topography of the coastal region (it is always assumed that the dead water is navigable). In very many cases it can be covered by the fire from another primary battery. Should this not be the case it might be necessary to instal a direct-fire battery ad hoc, which possibly might be able also to ful- fil one of the duties of secondary batteries, or to use mobile howitzers to cover the area. As regards the third disadvantage, adequate protection for the communications of the fire-control system, together possibly with its duplication, would seem to reduce the contingency of this breakdown to a negligible point.
All the primary batteries erected by the Germans on the Belgian coast were for indirect-fire. After the evacuation by the Allies of
