When first used the purpose of curtain fire was simply to guard or make possible the forward movement of the infantry and was kept well ahead of them, usually one or two hundred yards. It was also uniform all along the line as far as it extended; that is, if it moved ahead a hundred feet at one point it moved the same amount at every other point. It is a ticklish thing at first for men to advance upon the enemy's trenches with their own artillery booming away at their rear and shooting right over their own heads. But the trenches are seldom parallel. Often the country is rough and whereas the enemy may be dug in a hundred yards away at one point, it may be that fifty rods farther down the lines, the trenches are three hundred yards apart. In the main we speak of the lines being parallel, but as a matter of fact they very seldom are so. During the early days of the war if one of the opponents were going to make an attack he hammered the enemy's position with heavy guns which were concealed or camouflaged perhaps five miles behind the front line trenches. The bombardment lasted until it was assumed most of the enemy's soldiers had taken refuge in the dugouts and were so disorganized that they could not effectively resist. Besides this his trenches would be so battered that the chances of success for the well-planned assault would be the best. The time must be accurately arranged previously. All lieutenants and captains who directed the barrage must keep exact time and have watches timed to the second. My own brother, Brenton, is now a lieutenant of artillery and I had the pleasure of presenting him with a beautiful stop-watch before he went into action. At the given signal the barrage raised and the doughboys went over the top, hustled down the lanes which had been previously cut in their own barbed wire by the wiring party, made their way across No Man's Land, stooping low as they went, dropping flat to the ground every few yards, and trying to get to the trenches of the enemy before they could be stopped. But the machine guns of the enemy were found to be too formidable and destructive, and as a result of this experience they learned to use the light artillery which could continue its fire even while the attacking party were moving on, advancing as they advanced. The lighter field pieces were placed within a few hundred yards in the rear of the trenches and used to blind the Germans from protecting themselves, as well as to cover the advancing troops until they took the trench. Then the curtain fire was thrown still farther back behind the German line.