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Direct-Fire Batteries. Under certain circumstances it may be impossible to site a primary battery in a position concealed from the sea. It may have to be a direct-fire battery. In this case it should, if possible, be on a high site in order to facilitate fire with automatic sights at short range and also to render it less easy to hit. Since the guns will be visible from the sea every endeavour must be made to render them as bad targets as possible, by having nothing upstanding in the outline of the battery as seen from the sea. The essential point is that they must have a background. This may exist naturally, but, if not, an artificial background must be provided with an outline in keeping with the vicinity.

As regards ammunition storage it would still seem advisable to adopt the scheme of small dispersed expense stores with tramway communications to the guns, combined with small dumps in or near the gun emplacements for immediate use.

(b) Blockship Attack. Hitherto only the primary batteries have been considered for protection against bombardment, but there are the other possible forms of attack, which necessitate the use of secondary batteries of lighter guns. One of these is attack by blockships in order to seal up a harbour. This is pos- sible only where there is a very narrow channel which is to seaward of the important part of the harbour. For instance, there are the entrances to the harbours of Santiago de Cuba and Port Arthur, and to the Bruges ship canal at Zeebrugge. These were all attacked in modern times; the attempts made by the Amer- ican and Japanese navies respectively were unsuccessful, while at Zeebrugge the British attack succeeded.

Such attempts would always be made at night, and old war- ships would often be used for the purpose. This means that the time available for stopping the ships would be very short, and the feat is not to be accomplished easily. But they should be stopped before they reach the bottle-neck of the channel.

The defence guns must have a rapid rate of fire with good shell-power, and the means of illuminating the approaches must be the best possible. It may well be also that, in certain cases, torpedoes fired from the shore would prove effective. The guns need not be of the heaviest calibre, but nothing under a 6-in. gun will be of much use. The idea of protection for these guns requires very little consideration. In the dark there is little chance of direct hits on them, while shrapnel can be guarded against by light gun-shields. Such guns, and all secondary arma- ment, should be direct-fire, with automatic sights.

The succepsful'blocking of the Bruges ship canal on April 23 1918 is an excellent instance of the fact that a fleet, which is determined to come to close quarters with coast defences, will most surely find out any weak spot in the latter. There were weak spots at Xeebrugge. Most of the German guns were sited as if they were meant to defend the water outside the Mole, and none seemed to have been specifically allotted to deal with blockships, although the Germans quite realized the possibility of such a form of attack. The searchlights were sited similarly there was no concentration of illumination at the spot where the guns could have been certain of hitting. On the other hand the flanks of the canal entrance were crowded with machine-guns, trench mortars and rifles, some machine-guns being only 50 yd. from the final positions of the blockships. These weapons were of no use in stopping the ships, but were admirably placed for killing the crews, who, in leaving the ships, were completely exposed. That the losses amongst the crews of the blockships and the motor-boats were small can only be put down to the theory that " Fortune favours the brave."

(c) Close Torpedo Attack. Another form of close attack is that by small craft such as destroyers, torpedo-boats or motor craft, which would attempt to run in at night and attack ships at anchor inside a harbour, or dockgates, using the torpedo as- their main weapon. Here the question of the electric lights (see 6.601) is of primary importance. To stop such an attack secondary batteries are required. The guns of these batteries will have to possess increased shell-power compared with those previously in use, in order to keep pace with the greater protec- tion and greater speed now given to torpedo craft. This increase of speed gives less time for the shore guns to get in their hits, and therefore it is essential that each shell should have good de- structive effect. Wherever possible very low sites should not be used for secondary batteries. A certain height facilitates the use of automatic sights with the guns and favours observation of fire, and the guns are better enabled to see their target in the beams of the electric lights. However, it must be remem- bered that no dead water is permissible with these batteries, and

that the limit of navigable water is nearer the shore for light craft than for larger ships. Therefore, there are limits to the height at which secondary batteries should be placed, taking into account the angle of depression obtainable with the guns.

With an illuminated area of water it is generally not possible to bring an effective fire on torpedo craft at a greater range than 1,000 yd., at which range a height of 40 ft. is sufficient to allow automatic sights to be used effectively. While foggy weather would probably interfere with an attack of this nature some craft might try to take advantage of the obscuration of the lights and creep in. In such a case sound-ranging, especially sub-aqueous, a new method of posi- tion-finding produced by the war, could be profitably employed to ascertain the position of any such craft and allow a fairly accurate fire to be developed against it.

It seems probable, however, that modern conditions will render this form of attack less likely in the future than it was thought to be in the past. Still another form of it may have to be taken into account should the use of torpedoes from aircraft attain the sue-. cess which its advocates prophesy. Here the direction of approach of the enemy is not limited to a navigable channel, as the aircraft may descend from any quarter of the heavens. The defence against this modern phase is practically the general case of defence against any aircraft, except that the planes should be attacked as soon as possible before they have a chance to release their torpedoes. Also, they will be most likely to effect this release where their torpedoes have a fair run in the water against their targets.

(2) Defence of a Channel. Here the word channel is meant to imply a comparatively narrow stretch of water which has open or nearly open water at either end, the passage of which it is desired to bar to an enemy. Such channels as the Straits of Messina, the Straits of Shimonoseki, the Dardanelles and the Bosporus would come within the meaning. Also it may be taken to include harbours having a long channel of approach and a wide stretch of water inside the channel.

A fair number of cases in which such channels have been forti- fied and attacked have occurred in history. Not to go too far back, in 1807, a British squadron under sail forced the Dar- danelles in spite of the batteries. In this case and in similar cases in the past the outstanding feature has been that gun-fire alone has not been able to stop the passage of a determined fleet, where the ships have been able to pursue their course un- hindered by obstacles and where they could finally gain water unswept by gun-fire. Perhaps the most striking instance of such an operation was the passage of the Federal squadron under Farragut at Vicksburg on the Mississippi in 1863. The ships were slow and the current was swift, the navigation was not easy, the range was short and the guns were well-sited. But the squadron passed the town not once but several times. The defenders relied on their batteries only, no obstacles being placed in the river.

The World War produced a notable instance of this class of operation in the attempts of the British and French fleets to force the passage of the Dardanelles. Here the current is swift but the ships had greater speed than those of 1863. The Turkish batteries were certainly numerous but the guns were not up to date, and the batteries were generally badly sited and designed. But the Turks did not depend upon their guns only; they made extensive use of obstacles in the shape of submarine mines.

A desultory bombardment took place on Nov. 3 1914, but the real attack did not begin till Feb. 19 1915. The entrance to the Straits was gained and operations continued inside, culminating in the great attack on the main batteries near the Narrows on March 18 1915. In his despatches the British admiral states that the withdrawal of the ships was due to the menace of the mines. It may be said that the backbone of the defence was the minefields. Until they were removed the ships were hampered in their movements and could not deal properly with the batteries protecting the minefields; also the ships could not remove the mines until the protecting batteries were silenced. The attack of March 18 was not repeated.

It is possible and even probable that if the Turkish batteries had been of a modern pattern and had possessed proper range- finding appliances (the Germans added these afterwards) the shore guns might have played a larger part than they did, and this point should be remembered should similar operations take