The British now put armor on the car, mounted guns in it, and thus created a land battleship which was impervious to small artillery fire. The purpose was to tramp down the barbed wire entanglements, which hindered the infantry, to hunt down the German machine gun nests, walk right up to them and clean them out. It had been proved that artillery fire could not wipe out the underground dugouts. At Verdun there was under one of the hills a dugout, called the Crown Prince, eight hundred feet long and twelve feet high, in which a whole regiment might take refuge, and from which it could pour out when the defense was needed.

The first time the tanks went into action the Germans were astonished and the British troops were so delighted that they were hardly able to stand from laughter and joy. One of the correspondents thus described one of the first engagements. "A tank had been coming along slowly in a lumbering way, crawling over the interminable succession of shell craters, lurching over and down and into and out of old German trenches, nosing heavily into soft earth, and grunting up again, and sitting poised on broken parapets as though quite winded by this exercise, and then waddling forward in the wake of the infantry. It faced the ruins of the château and stared at them very steadily for quite a long time, as though wondering whether it should eat them or crush them. Our men were hiding behind ridges of shell craters, keeping low from the swish of the machine gun bullets and imploring the tank to 'get on with it.' Then it moved forward in a monstrous way, heaving itself on jerkily like a dragon with indigestion, but very fierce. Fire leaped from its nostrils. The German machine guns splashed its sides with bullets. . . . But it got on top of the enemy's trench, trudged down the length of it, laying its sand-bags flat and sweeping it with fire."

One tank would march up single-handed to a whole trench full of Germans. It would crawl around until it could rake it and thus force the whole company to surrender. When the infantry came up, it would hand over the prisoners, who stood there holding up their hands, and lollop off in search of new adventures. One tank took a town single-handed, driving the Germans into the cellars, and wandering undisputed up and down the streets. The machine gun bullets rattled on its sides like peas, but to no purpose. Another tank got stuck in the mud and the Germans rushed upon it. "They flung bombs at it, clambered on to its back, and tried to smash it with the butt ends of rifles, jabbed it with bayonets, fired revolvers and rifles at it." When the infantry arrived, between two and three hundred killed and wounded Germans lay on the ground around it. Presently, with a good deal of grunting and grinding, the tank heaved itself up and waddled off to find new foes.

But the tanks were at first not so effective as they were interesting. They were used at the Somme in September, 1916, and in the next year at Arras, Messines Ridge, and elsewhere, but were not really effective until the battle of Cambrai on November 20, 1917. The troops were here led against the Hindenburg Line by some hundreds of tanks on a thirty-two-mile front. The assault penetrated the German defenses to a depth of five miles, but inasmuch as the Hindenburg Line was here about twelve miles wide, they did not go through it. Nevertheless this was the largest single gain the Allies had made during the entire war.

It was a quiet part of the line, as the war went, and the surprise attack was therefore attempted against a relatively thinly held part of the German line. There could be no artillery preparation, for that would merely advertise what was coming. The ground was hard and dry and it was expected that the tanks would themselves be able to crush down the barbed wire, take the trenches, and perform the work usually done by the heavy artillery. Several hundred tanks were secretly, slowly concentrated along the thirty-two miles of front and hidden from the curious aëroplanes in woods and villages.

On November 20, the mists of the morning were extremely heavy, and out of them as day broke came trudging down upon the astonished Germans scores and hundreds of tanks. They trampled the barbed wire entanglements and slaughtered the Germans with a barrage of machine gun fire. Behind came the infantry, cheering, shouting, leaping, and laughing, and overhead was a tremendous barrage fire from the British heavy artillery, meant, now that the surprise was sprung, to crush the trenches immediately ahead of the tanks, to silence the German batteries, and to prevent the bringing up of reënforcements. The surprise was complete and the success astonishing. The Germans were killed or ran or surrendered, and the tanks and infantry rumbled gayly on, as line after line of the strong defenses fell.

Here had been concentrated great bodies of British cavalry. They were to ride round the infantry and tanks, once the formal defenses had been broken through, dash forward into the open country behind, and prevent the bringing up of reënforcements. The tanks and infantry moved slowly; the cavalry was to gallop, occupy as advanced positions as possible, and hold them until the infantry could come up. It was the first time in the war that great bodies of cavalry had been used for anything except scouting and the carrying of messages. The most picturesque element of the old warfare had practically disappeared from this war nor did the cavalry on this occasion accomplish much.

Great as was the success, it was not great enough. The British infantry outran their supplies, artillery, and reënforcements, and, before the position could be consolidated and defended, a fierce German counter-attack retook much of the ground. The technique of gaining ground in a hurry had been established. The technique of holding it had not yet been learned.