The most serious source of nationalist tension in Europe after 1871 was the area called the Balkans. This region was characterized by geographical and ethnic variation comprising modern-day Romania, Bulgaria, Albania, Greece, Macedonia, Croatia, Bosnia-Herzegovina, Slovenia, Serbia and Montenegro. Its inhabitants were broadly known as the Slavs.

A large part of the Balkans was under the control of the Ottoman Empire. Throughout the nineteenth century, the Ottoman Empire had sought to strengthen itself through modernisation and internal reforms but with very little success. The spread of the ideas of romantic nationalism in the Balkans together with the disintegration of the Ottoman Empire made this region very explosive.

As different Slavic nationalities struggled to define their identity and independence, the Balkan area became an area of intense conflict. The Balkan peoples based their claims for independence on nationality and used history to prove that they had once been independent but had subsequently been subjugated by foreign powers. They thought of their struggles as attempts to win back their long-lost independence.

The Balkan states were fiercely jealous of each other and each hoped to gain more territory at the expense of others. Matters were further complicated because the Balkans also became the scene of big power rivalry. European powers like Russia, Germany, England, and Austro-Hungary were keen on countering the hold of other powers and extending their own control. This led to a series of wars and finally the First World War.