TANKS. The name tank was given during the World War to the bullet-proof, armed vehicle, driven by mechanical power and capable of crossing rough country and obstacles by the use of caterpillar tracks. The name was first used in Dec. 1915 as a blind to conceal the true nature of the experimental fighting machine then being secretly constructed in England; after the first appear ance of the machine in the field the name was retained. To the British is due the credit of first conceiving and introducing this weapon which was destined to exert a decisive influence on the course of the War.
The development of firearms led to the virtual disuse of the fighting vehicle. The weight of armour which was necessary to provide protection was such that no armoured vehicle could be propelled across country by man-power or horse-power. The necessity for a fighting vehicle still existed and was in fact accentuated, especially with the introduction of the machine-gun ; there was, however, at the time no apparent solution to the me chanical construction of such a vehicle. As time progressed two inventions were developed and it was the combination of these that led to the construction of the tank. The two inventions were the caterpillar track and the high-speed internal-combustion en gine. The former enabled heavy vehicles to cross soft ground by the use of a track or endless belt so that the weight was distributed over a large area of ground ; the latter provided a light compact power unit by means of which the vehicle could be propelled. The combination produced tractors such as the Holt, invented and in common use in America before the War. Between 1907 and 1914 several inventors suggested that tractors of this nature should be constructed and provided with armour for use as a fight ing vehicle in war. No official action was, however, taken in this direction. The prevailing military opinion among all nations prior to 1914 was that any future war would be mainly a war of movement, and although it was realized that a frontal attack against a defensive position would be costly, it was considered that such an attack would be greatly assisted or even avoided entirely by envelopment or flank action.
The opening phases of the World War appeared to confirm these views, but in September the Germans fell back and took up a de fensive position on the Aisne and it was then that the great strength of modern field defences became apparent. The main source of strength of these defences lay in the machine-gun pro tected by an extensive use of barbed wire entanglements, and they proved to be impregnable to attack by troops, equipped as they were in 1914, without the most prodigal loss of life. The efforts of the French and British troops early in October to out flank the Germans in the north, led to an extension of these de fences right up to the sea. The Allies were then faced with a continuous defensive position without flanks that could be turned and they possessed no means of penetrating such defences. One solution of the difficulty appeared to be a large increase in the available artillery resources, particularly in the larger pieces and the provision of high-explosive shells. This solution was acted on at once and although no result could of course be expected for many months, it was hoped that sufficient artillery and ammuni tion would eventually be available to blast a way through the enemy defences and so re-establish the power of mobility.
Col. Swinton's Proposal.—Early in Oct. 1914 an officer of the Royal Engineers, Lt.-Col. (later Maj.-Gen.) E. D. Swinton, Royal Engineers, formed the opinion that a frontal assault against prepared positions, especially with limited artillery support, had become impossible, and that some form of power-driven protected machine which could traverse trenches and barbed wire was necessary to enable the attack to overcome the power of the defence. On Oct. 2o, 1914, Col. Swinton saw Col. (later Sir Maurice) Hankey, secretary of the Committee of Imperial De fence, and put forward his scheme which was briefly to develop the Holt tractor and produce a mobile armoured machine which should lead the assault and act as a machine-gun destroyer.