"Suddenly white wisps of smoke arise over the tree tops of a near-by forest; again the observer makes some entries and, while the aeroplane rushes furiously forward, marks down with his pencil one body of troops after another. Above a freight station another stop is made; on the platforms of its storehouses men rush along busily. Their work will have to be disturbed: a motion of the hand, a pull on the motor which starts the descent, a grasp for the third bomb--and a railway guardhouse collapses into itself. The last bomb hits its mark even better; it explodes right in the middle between two cars without, however, hurting anybody; for the workmen have run away as quickly as their feet will carry them; pillars of fire roar up high; gasoline or coal oil supplies apparently have been hit. To determine this definitely is impossible, for the aeroplane must rush on. After a short time, its commission executed, it turns back toward the east; the batteries which had been observed a short while ago and the lines of trenches are again passed and at last the tents of the hangar come into view; the cross, showing the place for landing, becomes visible; the descent begins; the wheels touch the ground with a sharp jolt; the observer jumps out of his seat and runs up to his commander to make his report." CHAPTER XXIX WINTER ON THE EASTERN FRONT By the end of November, 1915, winter had set in along the eastern front. Especially along the northern part of the eastern line this necessitated almost a complete stoppage of operations. For there the weather becomes very severe. The ground freezes sometimes to a depth of three and more feet, which, of course, makes it impossible to dig trenches quickly. But just as soon as trench digging at short notice became impossible operations had to cease. For whenever armies advance over closely contested ground--as was the case all along the eastern line--the advance by necessity is slow, possibly over only a few miles every day. And every time the line is pushed forward, and trenches previously occupied are left behind, it becomes necessary with each step of the advance to dig new trenches unless the advanced line was fortunate enough to be able to stop the day's work in the trenches of the enemy, a possibility which, of course, did not offer itself any too frequently. And even then a lot of digging was necessary, because what was previously, during the enemy's occupation, the back of a trench line now had to be turned into its front. All of this digging, or at least most of it, had to be done quickly, in order to avoid the loss of the newly gained positions by the success of hostile counterattacks. But both sides alike found it impossible to dig quickly, or, for that matter, in most cases to dig at all when the ground was frozen solid. So both sides found themselves condemned to a more or less continuous state of inactivity as far as all war operations were concerned, excepting only artillery duels, mining,