enveloping movement was very much restricted. The vast extent of their territory always made it possible for the Russians to effect a withdrawal. Their railway network, though of wide mesh, was extraordinarily favourable from a strategic point of view, and by its aid they were generally able to bring up reinforcements at the right time to any wing that was threatened, while, in the case of ourselves and our allies, our railway communications were not only very circuitous, but, when it came to a further advance, ceased altogether. In addition to this, with the extension of the Eastern theatre of war, a blow inflicted on one wing of the Russians could not have the same effect on the other sectors of their long front as would have been the case if it had been of less extent. Hence break-through tactics, which Napoleon attempted several times on the restricted battlefields of his age, supported by powerful heavy artillery, once again asserted their importance. Instances of this were furnished at Gorlice, in the later battles in Galicia, as well as between the Bug and the Vistula, in the breaking of the Russian Narew front in the summer of 1915, and in the break-through at Tarnopol in 1917. Also the Serbian and above all the Roumanian campaigns furnished several similar instances. The preliminary condition of success was always a moral and tactical superiority on the side of the attacker, and a corresponding violence of mass effect. The fact that we did not possess this moral and tactical superiority in sufficient measure in the West has always relegated to the background the idea of breaking through the enemy front. What has to be done is not only on a comparatively limited front to break in upon the enemy with concentrated masses--these masses will immediately be exposed to outflanking on both sides--but to force in a more or less considerable part of the enemy front, and then to develop strategically the break-through which has succeeded tactically. The extent of the success will in every case depend upon the local conditions and the strategic situation.