By the early 1900's the emergence of new nations such as Germany and Italy and the decline of old empires like Austria and Turkey had changed the former balance of power in Europe. Unrest in many nations within Austria-Hungary threatened the unity of the empire. Austria tried to dominate the Balkans in order to check the anti-Habsburg propaganda coming from Serbia.

Germany supported Austria's Balkan policy, for she herself planned to exploit the rich resources of Asia Minor and for that purpose needed a railway route through friendly territory in the Balkans. At the same time Russia was scheming for an extension of the Slav ascendancy to Constantinople and through Serbia to the Adriatic. Great Britain and France, despite the fact that they possessed the largest overseas empires, were disturbed lest some power might seek to obtain a 'place in the sun' at their expense. Imperialism thus produced conflicting national interests which made a great war possible.

The problem of Military Alliances

Related to the clash of imperialistic programs had been the construction of numerous entangling alliances. The pattern of alliances which divided Europe made each side less flexible than otherwise might have been the case. Germany backed Austria against the Serbs not so much because the Serbs interested Germany, but because the Austrian monarchy was the only ally Germany could count upon to help counterbalance the threat of encirclement by the rival alliance of France, Great Britain, and Russia. Similar calculations required the French to rally to the side of Russia in order to ensure Russian help against Germany in some future crisis.

The problem of Military Planning

By 1914 Europe had come to be divided into two rival groups of heavily armed powers. With the growth of military machines there developed in each country a general staff of experts, whose chief concern was to prevent the army of another power from 'getting the jump' on them in time of international crisis. These general staffs worked out carefully calculated 'timetables' of what must be done if war should break out. According to these mobilization plans, millions of reservists had to be called up from civilian life, issued equipment, and then be transported to the frontier as fast as available railway transport allowed.

The irony of the situation was that the more carefully every last railway car had been put to use by the mobilization plan, the more costly any modification of the plan became. Everybody wanted to be prepared to strike first, and in every international crisis there was always the danger that some chief of staff, in an effort to maintain the schedule on his 'timetable', might force an order of mobilization and thus precipitate war. As the fears and suspicions increased the proportion of national production devoted to make guns increased. Europe as a whole was never so well perpared to wage war as in the summer of 1914.
How the War started