The Balkan crises began in 1874. That year, Bosnia and Herzegovina rebelled against Ottoman rule, beginning the First Balkan Crisis. When Turkey refused to reform its governing structure, Serbia declared war on the Ottoman Empire on 30 June 1876. Russia, based on its foreign policy of pan-Slavism, or fraternal allegiance between all Slavic peoples of eastern Europe, declared war on the Ottomans in due course. Britain, interested in maintaining the balance of power and protecting its Mediterranean holdings that depended upon the status quo, nominally supported the Turkish sultan. On 31 January 1878, Sultan Hamid II of Turkey sought peace.
Otto von Bismarck hosted the peace conference, known as the Congress of Berlin. Britain, concerned that growing Russian power at the expense of the Ottoman Empire would tilt the balance of power in Russia's favor, secured Constantinople and the Balkans away from Moscow's dominion. Bosnia and Herzegovina were turned over to Austria-Hungary and Russia pledged to abandon its support of Serbia nationalism--all in the name of the balance of power. However, with Serbian claims disregarded, continued conflict lay in the future.
As a result of Russia's obvious political losses at the Congress of Berlin, Russia abandoned its alliance with Germany in the Three Emperors' League. Bismarck, in turn, recommitted Germany and Austria-Hungary together in a Dual Alliance in 1879. In 1882, Italy was asked to join the Dual Alliance, thus converting it into a Triple Alliance that lasted until the beginning of World War I in 1914. The balance of power seemed to be working.
When, in 1885, the Second Balkan Crisis erupted between Bulgaria and Serbia, Russia threatened to occupy Bulgaria, but Austria stepped in to prevent Russian dominance of the Balkans. When Germany supported Austria instead of Russia, the latter removed itself from all treaty obligations with Germany and allied itself with France in 1894. France, previously allied with Great Britain, cemented the Triple Entente when it encouraged the signing of an Anglo-Russian understanding in 1907. The balance of power now pitted Britain, France, and Russia against Germany, Austria-Hungary, and Italy.
In 1908, however, despite Russian objections, Austria-Hungary annexed Bosnia- Herzegovina outright. Serbia, along with Russia, believed that these Slavic lands should have been incorporated into a greater Serbian state. Eventually, Russia was forced to back down in the face of German pressure. Undaunted, Serbia took advantage of a weakened Turkey after a 1912 conflict with Italy to increase its Balkan holdings, causing the eruption of a war between Serbia and Bulgaria in 1913, known as the Third Balkan Crisis. Russia backed Serbia; Austria-Hungary backed Bulgaria. Though Britain nominally supported Russia and Germany tacitly supported Austria, both urged a peaceful resolution of the conflict. Regardless, Serbia was livid over both Austro-Hungarian support of Bulgaria and its continued dominance in Bosnia-Herzegovina, setting the stage for the spark that ignited World War I.
Consider two elements of European politics at the beginning of the twentieth century that made the balance of power so dangerous. The first is an unlikely culprit, but nevertheless important--namely, liberalism. If we define liberalism as Europe did in the nineteenth century, this political, economic, and philosophical doctrine referred to national self-betterment, the perfectibility of man, and the discoverability of natural rules of conduct that all men could understand and follow. Liberalism served to justify imperial conquest with the latter's potential to "civilize" the native populations; liberalism also recognized war, limited and quick, as a legitimate form of foreign policy. Throughout the nineteenth century, wars were localized, had spanned mere weeks, and were fought to preserve the balance of power. If that could be true of all war, the argument continued, war could serve both national and international good when fought properly. That is, when it was based on discoverable rules of conduct.