The two aviators, their planes much shot with holes but otherwise unhurt, rose suddenly, swooping in long circles to higher and yet higher altitudes. The first flushes of dawn were breaking. In the air two observation planes flying over the Allied front were signaling to the German batteries in the rear, from which came the barrage protecting their infantry from Allied advances. At once they knew what to do. Both drove on through the hostile fire and bore down upon these observation biplanes. Observation planes are not good fighters. In less than a minute after rising those two fighting planes had chased the larger, slower machines off the ground. But what was Blaine's surprise to see Bangs, not a hundred yards away, making bold signals strange code to the Germans back in the rear. Lafe himself could not read them. What did it mean? For an instant there flashed to him a suspicion that Bangs from Montana might not be just plain American. "I won't think such a thing!" thought Lafe. "What is he up to?" Then he saw that the enemy barrage was falling further back, just about where the recovering infantry was resuming its advance, after the short shock occasioned by the two raiding triplanes that had suddenly gone aloft. "Were the Allies in their turn assaulting the Boches? What could it mean? In another brief interval Blaine found out, when sudden demoralization set in at once. Without apparent cause the Boches, now nearly upon the first Allied trenches, found that they were the center of a bombardment from the rear. What did that mean? The fire was withering. Could the foe they were attacking be taking them in the flank? The idea was almost unbelievable. And yet the fire was also insupportable. With one accord the front lines recoiled, although their officers beat the privates with their sword flats, cursing and reviling them as cowards. Right on top of this, the queer noises in front materialized into certainties. The Allies were advancing. Were there not also reinforcements behind? Reinforcements hitherto kept back by what? The barrage. Where was that barrage now? Falling not only on their rear but also further back. How did this happen? Where were their own planes? Officers and men were dropping on every hand. A charging foe in front was almost on them. After a minute or two of this, that whole section of the advance appeared to melt like froth on the water. Meantime up above, and from a higher altitude than before, Bangs continued his mysterious signaling; not to Blaine or to the Allies, but -- wonder of all wonders -- to the Boches themselves. Blaine now understood this, for he had noticed that the barrage itself had fallen back. Instead of covering and protecting the Germans, it was slaughtering them even more than the two aviators had done with their machine guns from a lower altitude.