appear to be dependent upon other arms, and incapable of entirely independent action at all stages for reconnaissance, for overcoming anti-tank defence and for security. At the same time there is no doubt whatever about the immense reinforcement of offensive power which they have brought to the other arms. In themselves they combine mobility, fire and protection, each in a certain degree; moreover, they may solve many difficulties with regard to supply of ammunition, especially to cavalry. It has been amply proved that the great enemy to cavalry, and to infantry as well, is the machine-gun, and it is exactly against this weapon that tanks have proved themselves to be most efficient. Once a machine-gun is located in the open, i.e. almost anywhere except behind concrete defence, the tank can deal with it quickly and effectively, while guns heavy enough to destroy the tanks themselves should in their turn be dealt with by horse artillery. In this way each of the three arms will derive support and protection from the other, and all will derive information and active assistance from the air.
Aeroplanes will carry out both strategical and tactical reconnaissance, will locate the enemy's forces, and, so long as light lasts (an important reservation), will watch and report his movements. In action they will watch the progress of their own forces, look out for counter-movements, indicate in every possible way the nature of the enemy defences, and intervene in the fight, whenever possible, with bombs and rifle-fire. If any such cooperation is to be possible, the various arms must not only understand one another thoroughly, have been trained together and have established a mutual confidence, but they must have ample and efficient means of intercommunica- tion, which can only be by wireless telegraphy or telephony.
The same principles must apply to the employment of tanks with infantry and field (including heavy) artillery. Of all the difficulties which infantry has to overcome the two most dreaded are wire and machine-guns. In discussing the action of tanks with cavalry, rapid movement over comparatively open country has been assumed, but it is unlikely that this can be more than a preliminary phase of a few days' duration in a campaign where the belligerents are on even terms in matters of equipment. Heavy slow-moving troops will be rushed by rail to the frontier and will come into action within a few miles of railhead. Then will come the great struggle for the initiative, the result of which may well decide the whole war, and ruthless vigour will be demanded from troops and leaders. At this stage there will be great battles in which, as in August 1914, neither side will be completely on the defensive or completely on the offensive; but both, in their determination to reach rapid decision, will think chiefly of attack, and there will be comparatively few highly organized defences, other than those which may have been prepared in peace-time. Hastily prepared defences may be extremely effective against infantry, especially if well concealed. It is then that tanks, moving easily across country, crashing through hedges, crossing hollow roads, climbing embankments and making paths, easily and quickly, through hastily con- structed wire entanglements, will be of the utmost assistance to their accompanying infantry. In the stage of the campaign we have tried to imagine there will hardly have been time to construct land mines, the tank's greatest enemy, but the opposing infantry will be provided with heavier anti-tank rifles and more light field guns than are possible with cavalry. Possibly the tanks themselves may be more heavily armoured than those with the cavalry, where rapid movement is the ruling factor, but they cannot be entirely proof. They, like the cavalry tanks, will be dependent upon the air for information and upon artillery for support. Hence smoke screens, concealing the moving target from the defending guns, may be invaluable, as well as the moving barrage and the fire of guns told off to deal with special obstructions, batteries of emplacements which have been reported by aeroplanes or detected from air photographs. But since both sides will possess tanks, presumably approximately equal in numbers and efficiency, and since the tank is essentially an offensive weapon, it is probable that a new feature may be introduced into tactics, namely tank counter-strokes and tank
engagements, for on each side these machines will attempt to get at the enemy's infantry and protect its own. But with all their power for offensive action the tank still has grave limita- tions, for there are still obstacles to movement, such as the muddy banks of a sluggish stream, which they cannot overcome; mud, as the armies knew it in Flanders, is to the tank what uncut wire is to the infantry, and without power to move the tank is highly vulnerable. Valuable as they doubtless are, it is, therefore, easy to fall into the error of overestimating their possibilities, and it is important to bear in mind that they will not always have the moral effect upon infantry that they had when they were terrible and unfamiliar objects on the battle- field. They cannot turn hostile infantry out of even hastily prepared entrenchments; the most they can do is to make it comparatively easy for their own infantry to get in, and even to do so much they are themselves dependent upon the help of supporting artillery, while all arms are almost blind without the help of aeroplanes.
So far it may perhaps be possible to penetrate into the future, and to anticipate that the opening stages of the next great war between highly developed nations possessing con- tiguous frontiers will not be very unlike those of 1914 except that they will be fought out with more complicated machinery i and with even greater vigour. He would, however, have to be very bold who would venture to prophesy whether, with all the new inventions we now possess, or indeed with others of which we as yet know nothing, wars will really be short and decisions quick or whether prolonged passive resistance is still a possibility. Have the aeroplane and the tank, heavy artillery and the instantaneous fuze so strengthened the offence that it will be able to overcome any defence which human ingenuity can devise, and that there will be a return to the Napoleonic era, or will the defence again be able to assert its superiority as it did from the winter of 1914 to the summer of 1918? Is it again possible that aeroplanes, aided conceivably by artillery firing at extreme range, may wage war against the civil population with asphyxiating gases and heavy bombs, and render war so terrible and so destructive to life and property that field armies may cease to have their purpose? The answer would appear to be that one lesson which emerges from the late war is that there is no limit either to human ingenuity or to human endurance, and for that reason, if for no other, it is only prudent to assume that the balance between offence and defence will be as finely adjusted as ever in the past, and results will depend not upon engines but upon the brains and courage of those who use them.
Minor Wars. If we leave for a time the consideration of what may be termed first-class campaigns and turn to those of the second or third class, it would certainly seem as though science had rendered the advantage of civilized nations over uncivilized greater than ever before in both the strategical and tactical spheres. As has been shown, one great feature of differentiating first- from second-class campaigns is that of space and freedom of movement. Movement means power to concentrate with rapidity and secrecy and so to effect surprise. Now, it so happens that while campaigns of the first class have in the past been confined almost entirely to Europe, those against uncivilized or undeveloped races are conducted under the burning skies of Africa or Asia. Frequently the climate has been a more for- midable foe than the enemy, and the tribesmen or local levies have had far greater mobility than highly trained European infantry. Any device, therefore, which can add to mobility is enormously in favour of the civilized man, the product of industrial conditions. The campaign in Palestine gives the best possible example of tactical success directed against a ' suitable strategical objective. Victory when it came was absolute ; and complete, but it was over an enemy whose moral had been shaken through acting purely, or almost purely, on the defensive through four years of war. Against that enemy the British forces had won a series of tactical successes, but it was not until cavalry had secured full liberty of movement that tactical success was crowned by strategical victory. Against an enemy ill provided with special means of defence and with inferior
