A long line of flame flared up crimson in the pallid dawn. "Down, men, down!" shouted their officers, and the Yankee lads threw themselves flat on the ground while a leaden hail swept furiously over them. "Are you hurt, Bart?" cried Frank anxiously, as he heard a sharp exclamation from his comrade. "Not by a bullet," growled Bart. "Took some of the skin off my knee though when I went down." A second time the murderous fire came hurtling over them, but the officers noted with satisfaction that the enemy were shooting high. "They haven't got the range yet," observed Billy. "Up!" came the word of command, and again the men were on their feet and racing like mad toward the trench. They came at last to where it had been. For it was no longer a trench! Gone was the zigzag line that the boys knew by heart from having faced and fought against it for weeks. The mine had done its work thoroughly. Everywhere was a welter of hideous confusion. Barbed wire entanglements with their supporting posts had been rooted from the ground. Guns had been torn from their carriages. "Pill boxes" had been smashed to bits. Horses and men and wagons and camp kitchens were mingled together in wildest chaos. Parts of the trench had been filled to the surface with earth, while huge boulders blocked the entrance to some of the communicating passages. There were a few sharp fights with scattered units of the enemy that had retained their senses and were trying to get their machine guns into action. But these detachments were soon cut down or captured. The great majority of the survivors were so dazed that they surrendered with scarcely a show of resistance and were rounded up in squads to be sent to the rear. The first trench had been won, and it was almost a bloodless victory, only a few of the American troops having fallen in the sudden rush. But sterner work lay ahead, for the second and third German lines were still intact, bristling with men and supported heavily by their guns. "This was easy," grinned Billy. "Like taking a dead mouse from a blind kitten," chuckled Tom, as he wiped the grime and perspiration from his face. "Don't fool yourselves," warned Frank, as a shell came whining over their heads. "This was only a skirmish. The real fight is coming, and coming mighty quick!" CHAPTER II THE UPLIFTED KNIFE Even while Frank Sheldon spoke, the artillery of the enemy took on a deeper note until it reached the intensity of drumfire. But now the American gunners took a hand, and the shells came pouring over the heads of the boys, searching out the line of the second enemy trench and preparing the way for the advance. In obedience to commands, the American soldiers had sought shelter wherever they could find it, while they were recovering their wind. Only a moment could be granted for this, however, for time was everything just now. They had caught the enemy off his guard and must take advantage of the opportunity.