The first barrage, or curtain of fire, ever used to my knowledge was a feeble German effort in the Ypres salient in the autumn of 1914, though the French drum fire distributed over a certain area had, in a sense, a like effect. To make certain of clearness about fundamentals familiar to those at the front but to the general public only a symbol for something not understood, a curtain of fire is a swath of fragments and bullets from bursting projectiles which may stop a charge or prevent reserves from coming to the support of the front line. It is a barrier of death, the third rail of the battlefield. From the sky shrapnel descend with their showers of bullets, while the high explosives heave up the earth under foot. Shrapnel largely went out of fashion in the period when high explosives smashed in trenches and dugouts; but the answer was deeper dugouts too stoutly roofed to permit of penetration and shrapnel returned to play a leading part again, as we shall see in the description of a charge under an up-to-date curtain of fire in another chapter. Counter-battery work is another one of the gunner-general's cares, which requires, as it were, the assistance of the detective branch. Before you can fight you must find the enemy's guns in their hiding-places or take a chance on the probable location of his batteries, which will ordinarily seek every copse, every sunken road and every reverse slope. The interesting captured essay on British fighting methods, by General von Arnim, the general in command of the Germans opposite the British on the Somme, with its minutiae of directions indicative of how seriously he regarded the New Army, mentioned the superior means of reporting observations to the guns used by British aeroplanes and warned German gunners against taking what had formerly been obvious cover, because British artillery never failed to concentrate on those spots with disastrous results. Where aeroplanes easily detect lines, be they roads or a column of infantry, as I have said, a battery in the open with guns and gunners the tint of the landscape is not readily distinguishable at the high altitude to which anti-aircraft gunfire restricts aviators. When a concentration begins on a battery, either the gunners must go to their dugouts or run beyond the range of the shells until the "strafe" is over. If A could locate all of B's guns and had two thousand guns of his own to keep B's two thousand silenced by counter-battery work and two thousand additional to turn on B's infantry positions, it would be only a matter of continued charges under cover of curtains of fire until the survivors, under the gusts of shells with no support from their own guns, would yield against such ghastly, hopeless odds.