SHOCK troops are all that the name itself implies. They are the troops sent forward, in human waves, to receive and break the first shock of contact with the enemy lines. Invariably a large number of them are doomed to death or injury, and the men themselves know it. But the very knowledge seems to drive them forward with greater fury, and the clash, therefore, is one of carnage for one or both sides. These were the shock troops that were going over with the dawn against the entrenched Germans—if they still remained entrenched after the terrible fire to which they had been subjected for hours by the massed American artillery, augmented by the world-known French 75’s. Even through the rolling smoke screen the light was becoming stronger, and Tom, Ollie and Harper, plodding ahead rapidly with their comrades, knew that soon it would be full dawn, that the screen would be lifted, and behind a barrage of fire that still would precede them for a short distance, the infantry would come to position to launch its close-range avalanche of rifle and machine gun bullets upon the enemy. It was just as they were beginning to quicken the pace that Tom heard a grunt and a gasp, followed by a muttered word or two, and looking down upon his left side saw Ollie, almost up to his neck in a huge hole dug by one of the shells with which the Boche had made futile effort to stop the American fire. Tom on one side and George Harper on the other, they managed to haul Ollie out, but the sudden drop had jarred him to the point of nausea and for several yards, as they double-quicked it to catch up with their line, they virtually carried their chum along, each of them holding to one of his arms. Looking skyward Tom made another discovery. It was as though great flocks of giant birds peopled the air. Aeroplanes of every capacity and description and in various formations were maneuvering over their heads and beyond them. Watching them as he trotted along, Tom saw from time to time a smaller scout plane separate itself from its group and dart forward and out of sight over the enemy lines. Presently it would return, sometimes to remain with its squadron, at others to continue back to some signalling point in the rear, from which it relayed the facts of the German’s position or movements. Massive battle and bombing planes plowed along, their powerful motors beating a tremendous bass throb as their big propellers churned the air. Here and there, too, were anchored observation baloons, the observers in them, equipped with parachutes for a long jump to safety at any time, sitting at telephone instruments connected with the various headquarters. On the land and in the sky the battle was on—the history-making battle of the St. Mihiel salient!