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. [Illustration: The Polish Theatre of War.] When you examine the map you will be sure to notice that in all this western part of Russia there are but few railways for so large an area of country. There are also few good roads, for the country is so swampy that they are difficult to make and to keep passable. Without good roads and railways a modern army cannot keep the field; it cannot march, and it cannot supply itself with the necessary provision for men and guns. The general who has good roads and railways at his command can bring his men quickly and without great fatigue to the desired positions; he can move them rapidly to the points where he means to make his attacks, and he can supply himself promptly and continuously with food and ammunition. He can also bring up reinforcements rapidly, and carry his wounded and prisoners to the rear. Without good roads and railways he is greatly hampered. You can easily see that the Russian commander-in-chief has great difficulties to overcome because of the lack of good roads and railways in Poland. When, however, we turn to the German side of the frontier, quite a different picture presents itself. The Germans have always paid great attention to military railways, and have planned and constructed them throughout the empire with great diligence and foresight. It was by means of their splendid system of railways that they were able to mobilize their troops so quickly, and fling them without an hour's delay into Belgium. Behind the eastern frontier of Poland they have two double lines of railway, and these are united into a perfect gridiron by criss-cross lines. By means of this railway system they can carry their troops rapidly to any part of the frontier, and can readily supply themselves with food and ammunition. As we shall see later, the German generals have been able to transfer their men from the north to the south by railway, and have thus been enabled to carry out rapid movements which are quite impossible to the Russians.