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

A large part of the Balkans was under the control of the Ottoman Empire. The spread of the ideas of romantic nationalism in the Balkans together with the disintegration of the Ottoman Empire made this region very explosive.

The rebellious nationalities in the Balkans thought of their struggles as attempts to win back their long-lost independence. As the different Slavic nationalities struggled to define their identity and independence, the Balkan area became an area of intense conflict.

The Balkan states were fiercely jealous of each other and each hoped to gain more territory at the expense of the others.