Naturally in such a country roads are of prime importance in military operations.  A few built and maintained by the state are in excellent condition and practicable in all sorts of weather.  But for the rest communications consist of bridle paths and trails over the mountains.

As has been stated, the great highway from Belgrade to Saloniki is the key to all military operations in the Balkans; nor is this case any exception.  A study of the map will show how this big, underlying fact entered into the plans of the first three attempts at invading Serbia.  Naturally, had facilities been convenient at Belgrade, that would have been the point from which to advance.  The next possible point was over the Drina, because it was not so wide or so deep.

Bosnia and Herzegovina at the beginning of the war were sparsely served by railroads.  But for the purpose of an invasion of Serbia the lines running to Tuzla in the north and to Vishegrade and Uvatz in the south were of much strategic importance.  Moreover, unlike the Hungarian plain opposite Belgrade, the country is so mountainous and well wooded that great bodies of troops could be moved about without being observed.  We now come to the main reason why this point was chosen, next to Belgrade.  Though we shall see that they did not reach it at their first attempt, there is no doubt that the main objective of the Austrians was the little town of Valievo, lying some distance back from the Jadar and the field of battle.  For at Valievo is the terminus of a light railway which joins with the main line running from Belgrade down to Saloniki.  The Teutons were in a hurry to open this highway, for it meant opening a means of communication with the Turks, who were to become, and later did become, their active allies.  These are political matters of significance here insomuch as they explain the special importance of the railway from Belgrade south along the ancient highway of the Crusaders.

Before following this route farther south, a few words should be devoted to Montenegro.  Between Serbia and Montenegro lies the Sanjak of Novibazar.  This small territory nominally belonged to Turkey before the Balkan War, but it was in fact garrisoned by Austrian troops, the civil administration being left to the Turks.  Austria had gone to special trouble to establish this arrangement, so that it might have a wedge between the territories of the two little Serb nations.  Anticipating this war long ago, Austria had counted on having a large enough force in Novibazar to prevent a union of the two armies.  But, when it actually came, she was in no position to prevent it, so much of her strength being required to meet the Russians.

Montenegro is the natural refuge of the Serbs.  Whenever in the past they were especially hard pressed by the Turks, they would flee to the mountain fastnesses of Tzherna Gora, the Black Mountain, for here military operations, even in this day of modern artillery, are absolutely impossible, and when it came to mountain guerrilla fighting, the Turks were no match for the Serbs.  Thus it was that the Serbs were able to preserve their old traditions, their language and the best blood of their race.  And it may be said that to a slightly lesser extent Ragusa served the same purpose.