These advanced trenches were manned by comparatively small forces, whose duty it was to offer a sufficiently strong resistance to draw a fairly good-sized number of Germans. This purpose having been accomplished the troops in the advanced trenches would give way and retire by means of the communicating trenches into their main positions. Again and again the Germans followed them into the death-dealing hollow, to be decimated unmercifully in the manner described above. At the same time Russian guns would open fire and direct a sheet of shells toward the back of the attacker, thus cutting off most effectively any reenforcements which might have made it possible for the Germans to either storm the main trench or withdraw at least that part of their attacking party which had not yet fallen prey to Russian ingenuity. It is said that General Russky contrived to throw out fortifications of this nature around Dvinsk in an immense circle which had a diameter of twenty miles and with its circumference formed a front of almost two hundred miles. Of course, this front was not in the form of an unbroken line. There were any number of places along it that could be occupied by the Germans practically at will. But once there the next advance would invariably bring them face to face with a new obstacle, kill hundreds of them, and frequently result in the withdrawal of the remnant to its main line, from where another advance would be attempted promptly on the next day. One other feature of these fortifications contributed a great deal to their becoming practically impregnable. The Russian engineering troops saw to it that all these works were built as narrow as possible and were dug as deep as the ground permitted. It was this fact which made the German artillery fire so surprisingly ineffective at this point. In spite of its unceasing fierceness the results it accomplished were as nothing compared with the effort and expense it involved. For, of course, no matter how brilliant the gunnery, how wonderful the cannon, how devastating the shells, if the target at which they are aimed is sufficiently far away and sufficiently small, the result will be disappointing; and the Russians at Dvinsk saw to it that the Germans experienced a long series of costly and heartbreaking disappointments of that nature.