[Illustration: This picture gives you an idea of a typical landscape in Poland. Notice the difficulties which the Russians have had to overcome in bringing up food and ammunition to their armies.
From Sandomir the Vistula runs north and north-west across the high plateau of Southern Poland, in a broad valley hemmed in by wooded bluffs. Passing the Russian fortress of Ivangorod on its right bank, it afterwards receives the river Pilica on its left bank, and crosses the plain of Central and Northern Poland. About thirty miles north of the confluence with the Pilica is Warsaw,[28] the most important town in the whole of Russian Poland. It is a beautifully situated city, and before the war was one of the brightest and gayest places in Western Europe. A glance at the map will show you why it is so important both to the Russians and to the Germans. It is the meeting-place of three great Russian railways, by which alone men and ammunition can be carried swiftly into Russian Poland. Warsaw also commands the main stream of the Vistula, which the Russians largely use for transport. Were it to be captured, the communications of the Russians would be cut, and they would be powerless to meet the foe in Poland. Were the Germans to seize it and hold it, they could keep the Russians so far back from their frontier that all fear of invasion through Poland would vanish. Warsaw is the chief stronghold of Poland, and is one of the strongest citadels in Europe.
North of Warsaw the Vistula swings round to the west, and at the fortress of Novo Georgievsk receives the river Bug, which rises not far from Lemberg, and sweeps across the plain to the east of, and almost parallel with, the Vistula for more than two hundred miles. A right bank tributary of the Bug, the river Narew,[29] is worth notice, because along it we find a chain of Russian forts. About thirty miles west of Novo Georgievsk the Vistula receives on its left bank the sluggish river Bzura, which rises within a short distance of the Warta[30] or Warthe, a northward and westward flowing tributary of the German river Oder. The Vistula now sweeps north-west past Plock, and enters Prussia some ten miles above Thorn.
If you look carefully at Russian Poland, you will see that it forms a salient which projects into Germany and Austria for about two hundred miles from north to south, and two hundred and fifty miles from east to west. To the north of this salient is East Prussia, and to the south of it is the Austrian province of Galicia. Russian Poland can be entered by an enemy from the north, from the west, and from the south. If you look at the position of the forts (marked by stars on the map) you will see how Russia has prepared to meet invasions from these directions. A chain of forts from Novo Georgievsk north-east to Grodno on the Niemen bars the way into Russia from East Prussia. Warsaw and Ivangorod hold the line of the Vistula against an invasion from the west, and Ivangorod and Brest Litovski on the Bug stand in the road of troops advancing from Galicia. All these fortresses are linked up by railways.