They were of two kinds, the second of which has been, perhaps, unduly emphasized at the expense of the first.

The first was, that the Baltic extreme of this region lay at the very end of the longest possible line the Russians could move on. Even supposing their front extended (as soon it did) from the Carpathians to the sea, this Baltic piece was the end of the line and farthest from their material bases and their sources of equipment. It was badly served with railways, difficult of access from the soil lying to the east, and backed by that sparsely inhabited belt of Russian territory in which the modern capital of St. Petersburg has been artificially erected, but which is excentric to the vital process of Russia. As a fact, even after eight months of war, let alone in the first phases which we are here about to describe, the extreme end of this line was not attempted by the Russians at all.

Next to this extreme position, which was the first handicap, comes the region of the lakes, the nature of which was the second handicap.

The Masurian Lake district can best be appreciated by some description of its geology and its landscape. It was probably moulded by the work of ice in the past. Great masses of ice have ground out, in their very slow progress towards the sea over the very slight incline northwards of that line, hollows innumerable, and varying from small pools to considerable lakes; the ice has left, upon a background of sand, patches of clay, which hold the waters of all this countryside in brown stretches of shallow mere, and in wider extents of marsh and bog. The rare travellers who explore this confusion of low rounded swells and flats carry back with them to better lands a picture of one grossly monotonous type continuing day upon day. Pine and birch woods, often ordered with the regularity and industry of the German forest organization, but often also straggling and curiously stunted and small, break or confuse the view upon either side.

The impression of the district is most clearly conveyed from some sandy summit, bare of trees, whence a man may overlook, though not from any great height, the desolate landscape for some miles. He obtains from such a view neither the sense of forest which wooded lands of great height convey in spite of their clearings, nor the sense of endless plain which he would find farther to the east or to the north. He perceives through the singularly clear air in autumn brown heaths and plains set here and there with the great stretches of woodland and farmsteads, the stubble of which is soon confused by the eye in the distance with the barren heaths around. In winter, the undulating mass of deep and even snow is marked everywhere by the small, brown, leafless trees in their great groupings, and by the pines, as small, and weighted with the burden of the weather; but much the most striking of the things seen in such a landscape are the stretches of black water, or, if the season be hard, of black ice which, save when the snow has recently fallen, fierce winds will commonly have swept bare.

The military character of such a region will be clear. It is, in the technical language of military art, a labyrinth of defiles. Care has been expended upon the province, especially in the last two generations, and each narrow passage between the principal sheets of water carries a road, often a hard causeway. A considerable system of railways takes advantage of the same natural narrow issues; but even to those familiar with the country, the complexity of these narrow dry gates or defiles, and their comparative rarity (contrasted with the vast extent of waterlogged soil or of open pool), render an advance against any opposition perilous, and even an unopposed advance slow, and dependent upon very careful Staff work. Columns in their progress are for hours out of touch one with the other, and an unexpected check in some one narrow must be met by the force there present alone, for it will not be able to obtain immediate reinforcement.

Again, all this line, with its intermixture of sand and clay, which is due to its geological origin, is a collection of traps for any commander who has not thoroughly studied his lines of advance or of retreat—one might almost say for any commander who has not had long personal experience of the place. There will be across one mere a belt of sand or gravel, carrying the heaviest burdens through the shallow water as might a causeway. Its neighbour, with a surface precisely twin, with the same brown water, fringed by the same leaves and dreary stretches of stunted wood, will be deep in mud, but a natural platform may stretch into a lake and fail the column which uses it before the farther shore is reached. In the strongest platforms of this kind gaps of deep clay or mud unexpectedly appear. But even with these deceptions, a column is lucky which has only to deal in its march with open water and firm banks; for the whole place is sown with what were formerly the beds of smaller meres, and are now bogs hardened in places, in others still soft—the two types of soil hardly distinguishable.

During any orderly advance, an army proceeding through the Masurian Lakes will strictly confine itself to the great causeways and to the railway. During any retreat in which it is permitted to observe the same order it will be similarly confined to the only possible issues; but let the retreat be confused, and disaster at once threatens.

A congested column attempting to spread out to the right or to the left will fall into marsh. Guns which it has attempted to save by the crossing of a ford will sooner or later find mud and be abandoned. Men will be drowned in the unexpected deeps, transport embedded and lost; and apart from all this vast wastage, the confusion of units will speedily put such a brake upon the whole process of retirement that envelopment by an enemy who knows the district more thoroughly is hardly to be avoided.

It was this character in the dreary south of East Prussia which was the cause of Tannenberg, and as we read the strategical plan of that disaster, we must keep in mind the view so presented of an empty land, thus treacherous with marsh and reed and scrub and stretches of barren flat, which may be heath, or may be a horse's height and more of slightly covered slime.