Further details of the plan were that the artillery barrage of shrapnel and H.E. shell should open on the enemy's outpost at zero hour (6 :2O A.M.) and be advanced by stages of 250 yd. just ahead of the tanks and concentrated on special points. The tanks were to go forward at zero hour in sections of three machines, sections being allotted to different objectives according to the strength of the latter. Each section was composed of one vanguard tank and two main body tanks. The former was to lead and protect the advance of the two other machines, behind which followed the infantry in parties of varying size, marching in sections in single file. As the Hindenburg trenches, some 12 ft. wide, would have to be crossed each tank was to carry a specially made fascine 10 ft. long and 4j ft. in diameter to drop into the trenches to assist in the crossing. Special machines were fitted with drag grapnels in order to drag aside the wire en- tanglements which were known to be exceptionally thick and strong, for the passage of the cavalry. Great precautions were taken to maintain secrecy, upon which so much depended, and extremely careful preparations were made in the way of reconnaissance, the training of the infantry to act with the tanks, the movement of machines, and the formation of dumps of the necessary stores. For instance the preliminary movement of the tanks necessitated 36 special trains, and the material collected in dumps included 165,000 gal. of petrol, 55,000 Ib. of grease, 5,000,000 rounds of S.A.A. and 54,000 of 6-pdr. ammunition. Three brigades (nine battalions) of tanks took part in the attack, with two army corps of three divisions of the III. Army, a cavalry corps and 1,000 guns. In all there were 378 (Mark IV.) fighting tanks and 98 administrative machines.
Fog on the morning of Nov. 20 assisted the attack, which was carried out as arranged, the tanks following the barrage and the infantry the tanks. The operation was an amazing success and came as an absolute surprise to the enemy, most of whose infantry were panic stricken and bolted or surrendered, the garrisons of certain strong points alone offering a determined resistance. Assisted by the tanks, the infantry by evening had occupied Marcoing, 1 Bois des Neuf, Premy Chapel, Havrincourt, Graincourt, Aneux, Noyelles. Next day, and on the 23rd, 25th and 27th, further progress was made, but the tank units which had been fighting continuously were disor- ganized and the crews physically exhausted; and the mistake had been made of not keeping a small proportion of tanks in reserve. On the 27th the impetus of the attack died out with practically no more ground gained than had been won on the first day, where the tanks, starting from a base of 15,000 yd. length, had in 12 hr., and at a cost of some 4,000 casualties, enabled the enemy's zone to be penetrated to a depth of 12,000 yd. (at the third battle of Ypres an equal extent of penetration had taken three months), and 8,000 prisoners and 100 guns to be captured. And their action had ob- viated the necessity for a preliminary bombardment (which would have cut up the ground and rendered any rapid advance of infantry impossible, and brought a concentration of enemy's reserves), and also the usual wire cutting artillery fire, which together would have cost many millions of pounds. (An estimate places the cost of the preliminary bombardment at the third battle of Ypres at approx- imately 22,000,000. A similar bombardment at Cambrai would possibly have cost more, as the German wire was on the reverse slopes of the rising ground.)
In numbers the personnel of the tank corps employed in the fight amounted to a little over 4,000 of all ranks, or the strength of strong infantry brigade. The fact that there were no larger bodies of infantry ready to reinforce the tired troops and press the advantage gained, and that the cavalry did not break through to Cambrai as was intended, was not owing to any failure on the part of the tanks, which achieved more than had been promised. The absence of any large force to take advantage of the opening made by them tends to show that it was not believed that they could do what they actually did accomplish, and that their complete and extraordinarily speedy success was as much of a surprise to British Headquarters as it was to the Germans. For nearly three years efforts had been made by both sides to force a way through the enemy's position quickly. At Cambrai a door was suddenly flung open and there was no force to press through. The success achieved by the surprise counter- attack by the Germans on the 3Oth also had nothing to do with the previous action of the tanks, but its effect was to discount the whole British victory including their performance. Against the southern portion of this German counter-attack a brigade of tanks which were hurriedly collected proved their worth in a defensive r61e, and gave invaluable assistance in stopping the onrush of the enemy.
The success of the tanks at Cambrai on Nov. 20, and all that it implied, gave as much food for thought as had the first use of gas by the Germans in 1915, unattended, however, by the horror of the means employed on the first occasion when a sur- prise penetration was effected by either side. It has been de- scribed as the " Valmy of a new epoch in War, the epoch of the mechanical engineer." 2 But it is doubtful if the truth of this
- The information of the capture of this village was sent back by a
wireless signal tank, and was received at Albert 10 min. after the troops entered Marcoing.
- Tanks in the Great War, Col. J. F. C. Fuller, p. 153.
statement has been fully appreciated even three years after the war. Even so, the effect of this action on the Allies, and also, on the Germans, was immediate and far-reaching. It almost established the fact, for which the protagonists of the tank had been endeavouring to gain acceptance for many months, that the new Arm; used properly, was a serious factor in warfare which could not be put aside and ignored. And yet, though opinion in regard to the tanks had changed, even at that period when the immense losses suffered in the attempted offensives of the pre-i vious eighteen months had rendered the problem Of man-powerl so acute, the crucial point was still not realized that an actual saving in life and economy in man-power would be gained by the development and whole-hearted employment on a very large scale of the mechanical Arm. And steps were not at once taken for a great expansion. The increase of the Tank Corps pre-i viously deferred was agreed to; but a proposed further expansion,! based directly on the experiences of Cambrai, was not approved. ' And later, in April 1918, even the agreed increased establish-' ment was again temporarily suspended after the German; offensive in order to meet the demands for infantry reinforce- ments, and was not completed until after the striking successes gained by the tanks in July and Aug. 1918.
After Cambrai all ideas of attempting to prosecute the offen- sive were abandoned, and there ensued a period of preparation for resistance against the attack which was expected as the result of the reinforcement of the German strength on the west, rendered possible by the defection of Russia. To assist in' meeting this, the Tank Corps, now of five brigades, or thirteen battalions, with 320 Mark IV. and 50 Medium A machines fit. 1 for action, was in Feb. 1918 distributed in detachments over some 60 m. of front.
During the second battle of the Somme, from March 21 to the end of the month, the part played by it was to cooperate in various local ; counter-attacks, its action being generally useful in assisting to de- lay the enemy's advance, as the German infantry would not as a rule I face tanks until their guns were brought up. But out of the total, some 170 machines alone went into action usually and inevitably in hasty, improvised operations carried out during the general retrograde movement. Many machines were lost and their crews employed on foot as Lewis Gun sections. It was during this period i that the new " Whippet " machines made their debut with great ! effect. Generally speaking, the tanks were too scattered for full . value to be obtained from their action. The corps also took its share in repelling the second German thrust against the British, which started in the Lys area on April 9, during which three battal- ions fought, some of the personnel of the lost tanks fighting on foot as I a Lewis Gun brigade. It was in this quarter, near Villers Breton- neaux, that the first duel between tanks possibly a presage of | future warfare took place.
The lack of decisive results obtained by the small detach- ments of tanks acting in improvised counter-attacks in the general defensive seems to have revived the lingering prejudices of those who were hostile to the arm, and who maintained that the mass action of Cambrai could never be repeated. However, in spite of this, progress was made in May and June in preparing for the future offensive, the chief point of note being that trie new Mark V. (heavy) tanks, which were a great improvement i on previous models, being much handier and also more mobile, ; were arriving at the rate of 60 machines per week. On July 4 occurred the action which probably finally dispelled the doubts of the most conservative and reactionary. This was the sur- prise attack of Hamel, a deliberate offensive and not a defensive counter-attack, in which recently received Mark V. machines cooperated with the Australians. This fight was an example of a perfectly organized action and of the advantage of previous careful training to act together of tanks and infantry, and was a speedy and complete success, achieved at the low cost of some 700 casualties. One feature was the special power possessed > by the new and speedier tank of destroying machine-guns, many of which were rolled over and crushed.
The logic of facts was irresistible, and after this action the cooperation of the tanks was thenceforward accepted, not only as a useful adjunct but as an absolute necessity, for all offensive operations. On July 17, at the battle of Moreuil, one battalion of tanks cooperated with three French divisions in a most sue-
