TANKS
Tanks are moving fortresses containing light artillery, machine guns, and rifles, and while capable of inflicting heavy losses by fire they can also destroy obstacles, weapons, and personnel. Their garrisons are protected against the fire of small arms and from shrapnel bullets, but they are very vulnerable to other forms of artillery fire. Their mobility and radius of action are governed by the amount of petrol carried and by the physical endurance of the crew, but except over deep cuttings, {175} broad streams, swamps, very heavily shelled ground, rocky and mountainous country, or in thick woods they can move without difficulty. "The power of delivering successful surprise attacks against almost any type of defences is one of the most important advantages of the use of Tanks in large numbers" ("Field Service Regulations," vol. ii. (1921)).
During the First Battle of the Somme (September 1-November 18, 1916) "Our new heavily armoured cars, known as 'Tanks,' now brought into action for the first time, successfully co-operated with the infantry, and coming as a surprise to the enemy rank and file, gave valuable help in breaking down their resistance. . . . These cars proved of great value on various occasions, and the personnel in charge of them performed many deeds of remarkable valour" (Sir D. Haig's Dispatches).
AIRCRAFT
Two classes of Aircraft are used in the field. Aeroplanes, which are self-propelled and have an almost unlimited radius of action; and Kite Balloons, which, in favourable weather, can be towed by a lorry and can be moved frequently without loss of efficiency.
AEROPLANES are of the greatest value for reconnaissance and inter-communication, and not only obtain, and return to their base with, information of the highest value, but facilitate personal reconnaissance of the battlefield by commanders and staff officers. Their offensive and defensive action is also very great and the moral effect of their offensive action is of the highest value. Although aeroplane squadrons are mobile units they lose efficiency if the units are moved too frequently. The action of aircraft in various phases of fighting is dealt with throughout the Lectures.
KITE BALLOONS carry two observers, who can remain in telephonic communication with the ground up to a {176} height of 5,000 feet. Inflated balloons can be moved in favourable weather at a maximum speed of 8 miles an hour while at a height of about 500 feet. Their extreme vulnerability to artillery fire prevents their use close to the battle front.
GAS
"The advisability of employing gas as a military weapon is a matter for consideration by the authorities concerned before a campaign begins. Once authorised, however, and assuming that weather conditions are favourable, gas may be expected to play a part in every action. . . . The different methods in which gas can be employed make it a weapon which can be used by all arms, thus Artillery deal with gas shells, Infantry with light mortar gas bombs, Aircraft with aërial gas bombs, and Engineers with all methods of use that call for special manipulation" ("Field Service Regulations," vol. ii. (1921)).
Gas was introduced by the Germans during the Second Battle of Ypres (April 22-May 18, 1915), and the numerous experiments and trials necessary before gas can be used, and the great preparations which have to be made for its manufacture, show that its employment was not the result of a desperate decision, but had been prepared for deliberately. During the First Battle of the Somme (September 1-November 18, 1916) "the employment by the enemy of gas and liquid flame as weapons of offence compelled us not only to discover ways to protect our troops from their effects, but also to devise means to make use of the same instruments of destruction. . . . Since we have been compelled, in self-defence, to use similar methods, it is satisfactory to be able to record, on the evidence of prisoners, of documents captured, and of our own observation, that the enemy has suffered heavy casualties from our gas attacks, while the means of protection adopted by us {177} have proved thoroughly effective" (Sir D. Haig's Dispatches).