In studying the military movements in a country of this character, special attention must be paid to the railway lines.  Railways, and more especially those running parallel to the fronts, are absolutely necessary to success.  In looking, therefore, for a key to the object of any particular movement, the first step must be a close study of this railroad situation.

We find from Riga to the fortress of Rovno there is a continuous line of railroad, running generally north and south and passing through Dvinsk, Vilna, Lida, Rovno, and thence down through Poland to Lemberg.  Every effort of the Russian armies in the succeeding chapters will be made to keep to the westward of and parallel to this line, and for a very good reason.

Feeding into this great north and south artery are the branch lines from Petrograd to Dvinsk; from Moscow to the junction at Baranovitschi; from Kiev to Sarny.  Aside from these three important branch lines, there are a few other single-track offshoots, but from a military point of view they are of no importance.

This line was the main objective (short of capturing Riga itself) of the German operations.  This line proves especially vital to the Russians, for nowhere east of it is there another such line which could be used for the same purpose.

If, in the campaigns to be described, this railroad falls into Russian hands, it gives every facility for strengthening or reenforcing any part of the Russian front where German pressure becomes excessive.  It is, in addition, a solution to the difficult problem of transportation of supplies.  To use a military term, it gives the Russian army a mobility not possessed by the enemy because of a lack of similar facilities.

But should this railroad be taken by the Germans, the advantage would immediately be reversed.  And if once the Russian lines were driven back beyond the railroad, a division of their forces would be forced upon them; their armies would be obliged to group themselves beside the three east and west branches already mentioned, for only by these three systems could their forces be supplied, lateral communications being absolutely lacking.  And this is the key to the fighting, not only in the northern section of the front, but all along the line, down to Galicia.  Naturally, only the Russian railroads need be considered, for in the first months of the war the Germans are the invaders in the northern half of the eastern front, except for a few short periods in the beginning.  Compared to the German railway lines near the frontier, the Russian lines are very few.

There are two distinct railway lines running from Germany into East Prussia, with innumerable branches leading to all points of the Russian frontier, laid especially for military purposes.  It was along these that we shall witness the German forces rushed from Belgium to drive back the first Russian advance.  But, of course, the moment the Germans enter Russian territory they have no advantage over the Russians, since even their wonderful efficiency does not enable them to build railroads as fast as an army can advance.  Hence, we observe their efforts to gain possession of the Russian railroads.