There is no race-horse that can keep up with an automobile, no deer that can out-run a locomotive. A bicyclist can soon tire out the hardiest of hounds. Why? Because animals run on legs, while machines run on wheels.

As wheels are so much more speedy than legs, it seems odd that we do not find this form of locomotion in nature. There are many animals that owe their very existence to the fact that they can run fast. Why hasn't nature put them on wheels so that when their enemy appears they can roll away, sedately, instead of having to jerk their legs frantically back and forth at the rate of a hundred strokes a minute?

But one thing we must not overlook. Our wheeled machines must have a special road prepared for them, either a macadam highway or a steel track. They are absolutely helpless when they are obliged to travel over rough country. No wheeled vehicle can run through fields broken by ditches and swampy spots, or over ground obstructed with boulders and tree-stumps.

But it is not always possible or practicable to build a road for the machines to travel upon, and it is necessary to have some sort of self-propelled vehicle that can travel over all kinds of ground.

Some time ago a British inventor developed a machine with large wheels on which were mounted the equivalent of feet. As the wheels revolved, these feet would be planted firmly on the ground, one after the other, and the machine would proceed step by step. It could travel over comparatively rough ground, and could actually walk up a flight of stairs. We have a very curious walking-machine in this country. It is a big dredge provided with two broad feet and a "swivel chair." The machine makes progress by alternately planting its feet on the ground, lifting itself up, chair and all, pushing itself forward, and sitting down again.

Although many other types of walking-machines have been patented, none of them has amounted to very much. Clearly, nature hopelessly outclasses us in this form of propulsion.

Years ago it occured to one ingenious man that if wheeled machines must have tracks or roads for their wheels to run on, they might be allowed to lay their own tracks. And so he arranged his track in the form of an endless chain of plates that ran around the wheels of his machine. The wheels merely rolled on this chain, and as they progressed, new links of the track were laid down before them and the links they had passed over were picked up behind them. A number of inventors worked on this idea, but one man in particular, Benjamin Holt, of Peoria, Illinois, brought the invention to a high state of perfection. He arranged a series of wheels along the chain track, each carrying a share of the load of the machine, and each mounted on springs so that it would yield to any unevenness of the ground, just as a caterpillar conforms itself to the hills and dales of the surface it creeps over. In fact, the machine was called a "caterpillar" tractor because of its crawling locomotion.

But it was no worm of a machine. In power it was a very elephant. It could haul loads that would tax the strength of scores of horses. Stumps and boulders were no obstacles in its path. Even ditches could not bar its progress. The machine would waddle down one bank and up the other without the slightest difficulty. It was easily steered; in fact, it could turn around in its own length by traveling forward on one of its chains, or traction-belts, and backward on the other. The machine was particularly adapted to travel on soft or plowed ground, because the broad traction-belts gave it a very wide bearing and spread its weight over a large surface. It was set to work on large farms, hauling gangs of plows and cultivators. Little did Mr. Holt think, as he watched his powerful mechanical elephants at work on the vast Western wheat-fields, that they, or rather their offspring, would some day play a leading role in a war that would rack the whole world.

But we are getting ahead of our story. To start at the very beginning, we must go back to the time when the first savage warrior used a plank of wood to protect himself from the rocks hurled by his enemy. This was the start of the never-ending competition between arms and armor. As the weapons of offense developed from stone to spear, to arrow, to arquebus, the wooden plank developed into a shield of brass and then of steel; and then, since a separate shield became too bothersome to carry, it was converted into armor that the warrior could wear and so have both hands free for battle. For every improvement in arms there was a corresponding improvement in armor.

After gunpowder was invented, the idea of armor for men began to wane, because no armor could be built strong enough to ward off the rifle-bullet and at the same time light enough for a man to wear. The struggle between arms and armor was then confined to the big guns and the steel protection of forts and war-ships.

But not so long ago the machine-gun was invented, and this introduced a new phase of warfare. Not more than one rifle-bullet in a thousand finds its mark on the battle-field. The Boers in the battle of Colenso established a record with one hit in six hundred shots. In the excitement of battle men are too nervous to take careful aim and they are apt to fire either too high or too low, so that the mortality is not nearly so great as some would expect. But with the machine-gun there is not this waste of ammunition, because it fires a stream of bullets, the effect of which can readily be determined by the man who operates the volley. The difference between the machine-gun fire and rifle fire is something like the difference between hitting a tin can with a stone or with a stream of water. It is no easy matter to score a hit with the stone; but any one can train a garden hose on the can, because he can see where the water is striking and move his hose accordingly until he covers the desired spot. In the same way, with the machine-gun, it is much easier to train the stream of bullets upon the mark, and, having once found the mark, to hold the aim. That is one reason why the destruction of a machine-gun is so tremendous; another, of course, being that it will discharge so many more shots per minute than the common rifle.

In the Russo-Japanese War, the Russians played havoc with the attacking Japanese at Port Arthur by using carefully concealed machine-guns, and the German military attachÉs were quick to note the value of the machine-gun. Secretely they manufactured large numbers of machine-guns and established a special branch of service to handle the guns, and they developed the science of using them with telling effect. And so, when the recent great war suddenly broke out, they surprised the world with the countless number of machine-guns they possessed and the efficient use to which they put them. Thousands of British soldiers in the early days of the war fell victims to these death-dealing machines. Two or three men with a machine-gun could defy several companies of soldiers, especially when the attackers had to cut their way through barbed wire entanglements. It was clearly evident that something must be done to defend the men against the machine-gun; for to charge against it meant, simply, wholesale slaughter.

At first the only means of combating the machine-guns seemed to be to destroy them with shell-fire; but they were carefully concealed, and it was difficult to search them out. Only by long-continued bombardment was it possible to destroy them and tear away the barbed wire sufficiently to permit of a charge. Before an enemy position was stormed it was subjected to the fire of thousands of guns of all calibers for hours and even days.

But this resulted in notifying the enemy that a charge was ere long to be attempted at a certain place, and he could assemble his reserves for a counter-attack. Furthermore, the Germans learned to conceal their machine-guns in dugouts twenty or thirty feet underground, where they were safe from the fire of the big guns, and then, when the fire let up, the weapons would be dragged up to the surface in time to mow down the approaching infantry.

It was very clear that something would have to be done to combat the machine-gun. If the necessary armor was too heavy for the men to carry, it must carry itself. Armored automobiles were of no service at all, because they could not possibly travel over the shell-pitted ground of No Man's Land. The Russians tried a big steel shield mounted on wheels, which a squad of soldiers would push ahead of them, but their plan failed because the wheels would get stuck in shell-holes. A one-man shield on wheels was tried by the British. Under its shelter a man could steal up to the barbed wire and cut it and even crawl up to a machine-gun emplacement and destroy it with a hand-grenade. But this did not prove very successful, either, because the wheels did not take kindly to the rough ground of the battle-field.

And here is where we come back to Mr. Holt's mechanical elephants. Just before the great war broke out, Belgium—poor unsuspecting Belgium—was holding an agricultural exhibit. An American tractor was on exhibition. It was the one developed by Mr. Holt, and its remarkable performances gained for it a reputation that spread far and wide. Colonel E.D. Swinton of the British Army heard of the peculiar machine, and immediately realized the advantages of an armored tractor for battle over torn ground. But in the first few months of the war that ensued, this idea was forgotten, until the effectiveness of the machine-gun and the necessity for overcoming it recalled the matter to his mind. At his suggestion a caterpillar tractor was procured, and the military engineers set themselves to the task of designing an armored body to ride on the caterpillar-tractor belts. Of course the machine had to be entirely re-designed. The tractor was built for hauling loads, and not to climb out of deep shell-holes; but by running the traction-belts over the entire body of the car, and running the forward part of the tractor up at a sharp angle the engineers overcame that difficulty.

In war, absolute secrecy is essential to the success of any invention, and the British engineers were determined to let no inkling of the new armored automobiles reach the enemy. Different parts of the machines were made in different factories, so that no one would have an idea of what the whole would look like. At first the new machine was known as a "land-cruiser" or "land-ship"; but it was feared that this very name would give a clue to spies, and so any descriptive name was forbidden. Many of the parts consisted of rolled steel plates which might readily be used in building up vessels to hold water or gasolene; and to give the impression that such vessels were being constructed the name "tank" was adopted. The necessity of guarding even the name of the machines was shown later, when rumors leaked out that the tanks were being built to carry water over the desert regions of Mesopotamia and Egypt. Another curious rumor was that the machines were snow-plows for use in Russia. To give some semblance of truth to this story, the parts were carefully labeled, "For Petrograd."

Probably never was a military secret so well guarded as this one, and when, on September 15, 1916, the waddling steel tractors loomed up out of the morning mists, the German fighters were taken completely by surprise. Two days before, their airmen had noticed some peculiar machines which they supposed were armored automobiles. They had no idea, however, that such formidable monsters were about to descend upon them.

The tanks proceeded leisurely over the shell-torn regions of No Man's Land, wallowing down into shell-holes and clambering up out of them with perfect ease. They straddled the trenches and paused to pour down them streams of machine-gun bullets. Wire entanglements were nothing to them; under their weight steel wire snapped like thread. The big brutes marched up and down the lines of wire, treading them down into the ground and clearing the way for the infantry. Even trees were no barrier to these tanks. Of course they did not attack large ones, but the smallish trees were simply broken down before their onslaughts. As for concrete emplacements for machine-guns, the tanks merely rode over them and crushed them. Those who attempted to defend themselves in the ruins of buildings found that the tanks could plow right through walls and bring them down in a shower of bricks and stone. There was no stopping these monsters, and the Germans fled in consternation before them.

There were two sizes of tanks. The larger ones aimed to destroy the machine-gun emplacements, and they were fitted up with guns for firing a shell. The smaller tanks, armed with machine-guns, devoted themselves to fighting the infantry. British soldiers following in the wake of the bullet-proof tank were protected from the shots of the enemy and were ready to attack him with bayonets when the time was ripe. But the tanks also furnished an indirect protection for the troops. It was not necessary for the men to conceal themselves behind the big tractors. Naturally, every Hun who stood his ground and fought, directed all his fire upon the tanks, leaving the British infantry free to charge virtually unmolested. The success of the tank was most pronounced.

In the meantime the French had been informed of the plans of their allies, and they set to work on a different design of tractor. It was not until six months later that their machines saw service. The French design differed from the British mainly in having the tractor belt confined to the wheels instead of running over the entire body of the tank. It was more blunt than the British and was provided at the forward end with a steel cutting-edge, which adapted it to break its way through wire entanglements. At each end there are two upward-turning skids which helped the tank to lift itself out of a hole. The larger machines carried a regular 75-millimeter (3-inch) field-gun, which is a very formidable weapon. They carried a crew of one officer and seven men.

Life in a tank is far from pleasant. The heat and the noise of machinery and guns are terrific. Naturally, ventilation is poor and the fumes and gases that accumulate are most annoying, to say the least. Sometimes the men were overcome by them. But war is war, and such discomforts had to be endured. But the tank possessed one serious defect which the Germans were not slow to discover. Its armor was proof against machine-gun fire, but it could not ward off the shells of field-guns, and it was such a slow traveler that the enemy did not find it a very difficult task to hit it with a rapid-fire gun if the gunner could see his target. And so the Germans ordered up their guns to the front lines, where they could score direct hits. Only light guns were used for this purpose, especially those whose rifling was worn down by long service, because long range was not necessary for tank fighting.

When the Germans began their final great drive, it was rumored that they had built some monster tanks that were far more formidable than anything the Allies had produced. Unlike the British, they used the tanks not to lead the army but to follow and destroy small nests of French and British that were left behind. When the French finally did capture one of the German tanks, which had fallen into a quarry, it proved to be a poor imitation. It was an ugly-looking affair, very heavy and cumbersome. Owing to the scarcity of materials for producing high-grade armor, it had to make up in thickness of plating what it lacked in quality of steel. The tank was intended to carry a crew of eighteen men and it fairly bristled with guns, but it could not manoeuver as well as the British tank; for when some weeks later a fleet of German tanks encountered a fleet of heavy British tanks, the Hun machines were completely routed.

It was then that the British sprang another surprise upon the Germans. After the big fellows had done their work, a lot of baby tanks appeared on the scene and chased the German infantry. These little tanks could travel at a speed of twelve miles an hour, which is about as fast as an ordinary man can run. "Whippets," the British called them, because they were like the speedy little dogs of that name. They carried but two men, one to guide the tank and the other to operate the machine-gun. The French, too, built a light "mosquito" tank, which was even smaller than the British tank, and fully as fast. It was with these machines, which could dart about quickly on the battle-field and dodge the shell of the field-guns, and which were immune to the fire of the machine-gun, that the Allies were able to make progress against the Germans.

When the Germans retired, they left behind them nests of machine-guns to cover the withdrawal of their armies. These gunners were ordered to fight to the very end. They looked for no mercy and expected no help. Had it not been for the light tanks, it would have been well nigh impossible to overcome these determined bodies of men without frightful losses.

Since America invented the machine-gun and also barbed wire, and since America furnished the inspiration for the tank with which to trample down the wire entanglements and stamp out the machine-guns, naturally people expected our army to come out with something better than anything produced by our allies. We did turn out a number of heavy machines patterned after the original British tank, with armor that could stand up against heavy fire, and we also produced a small and very speedy tank similar to the French "baby" tank, but before we could put these into service the war ended. The tanks we did use so effectively at St.-Mihiel and in the Argonne Forest were supplied by the French.