Raiding parties were active on both sides, as each was eager to get prisoners and information, and scarcely a night passed without heavy skirmishes between patrols that in former days would have risen to the dignity of battles. Overhead the sky was dotted with the planes of the rival forces and the hum of the motors of the giant birds of prey was continuous. They fought not only in single combat but in sauacfrons, and the sight of one or more whirling down in flames was so common that it scarcely attracted attention. And most ominous of all, the medical service was organizing gigantic units close to the front, in anticipation of the harvest of blood and wounds that was so close at hand. Yes, a battle was coming. The grim reaper was sharpening his scythe and the watching world was waiting for the outcome in an agony of expectation. The forces as far as known were evenly balanced, though it was rumored that the Germans were drawing large reserves temporarily from the eastern front, and color was lent to this by the fact that the Swiss frontier had been closed for a month to conceal the movement of troops. It was not yet certain which side would make the first move. Each army was drawn up in a strong natural position with ranges of hills behind in the event of having to fall back. "I hope we get in the first blow," remarked Frank, as he discussed the question with his chums. "So do I," agreed Bart. "You know then where you're going to strike. This matter of fighting behind entanglements doesn't make a hit with me at all." "There's more of a swing and rush to it when you attack," commented Billy. "Do you remember how it was, fellows, in that last big scrap when we were sprinting over No Man's Land? You're so eager to get at the Huns that you don't have time to think of danger." But one foggy morning not long after, the German leaders settled the matter for the Camport strategists and struck with tremendous force at the Allied lines. Two hours before dawn the German guns opened up with a roar that shook the earth. The air was full of flying shells; tear shells to blind the eyes of the Allied gunners so that they could not see to serve their pieces; mustard shells that bit into the lungs like a consuming fire; chlorine gas shells, with a deadly poison, to cause such agony that even surgeons, hardened in the exercise of their profession, turned away their faces from the writhings of the victims. Then, following these, a storm of leaden hail, withering, searing, blasting, before which it seemed no living thing could stand. Crouched low in their trenches, massed line behind line, the Allied forces bent their heads to the storm, and waited in grim fury for the infantry attack that they knew would surely follow. And it was not long in coming. The fog had risen by this time, and over the fields, rank upon rank, marching at the double quick, came masses of gray figures that seemed as endless as the waves of the sea.