The training of the Americans was also in modern efficiency that made America prominent in the world of industry. The reduction of the German salient at St. Mihiel was an object lesson to the Germans in American methods. General Pershing commanding that operation in person, assembled the newspaper correspondents the day before the drive. Maps were shown, giving the extent and locale of the attack. The correspondents were invited to follow the American troops and a time schedule for the advance was given to the various corps commanders. In that operation, 152 square miles of territory and 72 villages were captured outright. For the reduction of the German defenses and for the creeping barrage preceding the American advance, more than 1,500,000 shells were fired by the artillery. Approximately 100,000 detail maps and 40,000 photographs prepared largely from aerial observations, were issued for the guidance of the artillery and the infantry. These maps and photographs detailed all the natural and artificial defenses of the entire salient. More than 5,000 miles of telephone wire was laid by American engineers immediately preceding the attack, and as the Americans advanced on the morning of the battle, September 12, 1918, 6,000 telephone instruments were connected with this wire. Ten thousand men were engaged in operating the hastily constructed telephone system; 3,000 carrier pigeons supplemented this work. During the battle American airplanes swept the skies clear of enemy aircraft and signalled instructions to the artillery, besides attacking the moving infantry, artillery and supply trains of the enemy. So sure were the Americans of their success that moving-picture operators took more than 10,000 feet of moving-picture film showing the rout of the Germans. Four thousand eight hundred trucks carried food, men and munitions into the lines. Miles of American railroads, both of standard and narrow gauge, carrying American-made equipment, assisted in the transportation of men and supplies. Hospital facilities including 35 hospital trains, 16,000 beds in the advanced sector, and 55,000 other beds back of the fighting line, were prepared. Less than ten per cent of this hospital equipment was used. As the direct consequence of this preparation, which far outstripped anything that any other nation had attempted in a similar offensive, the Americans with a remarkably small casualty list took 15,188 prisoners, 111 guns, many of them of large calibre, immense quantities of munitions and other supplies, and inflicted heavy death losses upon the fleeing Germans. Two selective service laws operated as manhood conscription. The first of these took men between the ages of twenty-one and thirty-one years inclusive. June 5, 1917, was fixed as registration day. The total number enrolled was 9,586,508. The first selective army drawn from this number was 625,000 men.