German troops were therefore concentrated near the points chosen for attack, and this was done with the utmost secrecy, the troop trains running unlighted at night, so as to escape the observation of Allied aviators. Two hundred divisions in all were gathered for the German drive, and fully half of them were assembled near the British front on the Somme. March 21 was set as the date for the attack and every precaution was taken to render it a surprise to the British. The German troops were led to believe that they would be irresistible, and that Paris, their long-looked-for goal, would soon be won. Meanwhile the Allies had not been idle. Expecting the drive, but not knowing where it would strike first, preparations had been made all along the line, not merely for strenuous defense of the positions held, but also for eventualities in case of enforced retreat. New positions back of the lines were prepared, reserves were distributed at strategic points, and full co-operation between the Allied armies was arranged for. The British took over the section of the French front between St. Quentin and Chauny, in addition to their former front, and by so doing relieved the strain on the far-flung French line. The Germans counted for victory upon their concentration of vast bodies of troops and the element of surprise, hoping to break through between the British and French armies before Allied reserves could be brought up in sufficient numbers to halt them. OPENING DATS OF THE BATTLE On the day set, Thursday, March 21, the great battle opened, after a six-hour bombardment, the British 3rd and 5th armies being attacked simultaneously. The German infantry advanced in waves, of which there seemed no end, and these were followed by batteries of trench mortars, until the front line of German trenches had been reached. Then, wave after wave, the advance was continued, in the face of a furious British fire, until the defenders were compelled to draw back through sheer force and weight of numbers. The German waves moved forward at the calculated rate of 200 yards every four minutes, wherever it was found possible to do so. Each wave, on reaching its objective point, dropped to the ground and opened fire with rifles and machine guns, placing a barrage 2,000 yards ahead of them, under cover of which the succeeding wave advanced. Thus each wave passed over the one ahead of it, and fresh troops were constantly coming to the front. With such tactics, against a spirited and determined foe, the losses of the attackers were naturally enormous. In fact, it was estimated that the casualties suffered by the Germans during the first few days of such fighting amounted to 250, men. But, driven on by ruthless commanders, they continued to advance in masses, though mowed down by the British at every successive step.