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. [Illustration: (C) Underwood & Underwood British Tank Climbing out of a Trench at Cambrai] 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. [Illustration: (C) Underwood & Underwood Even Trees were no Barrier to the British Tank] [Illustration: Press Illustrating Service The German Tank was very heavy and cumbersome]