Throughout the 19th and early 20th century, the Ottoman Empire had lost land in the Balkans to the peoples who lived there. The Great Powers were also interested in extending their influence in the region.

 

Austrian and Russian relations were poor over their rivalry in the Balkans. Both hoped to expand there at the expense of the Ottoman Empire. Another important factor was the growth of Slav nationalism among the people who lived there, especially Serbia. Russia encouraged Slav nationalism while Austria worried that this nationalism could undermine her empire. Russia supported Serbia which was very bitter at the annexation of Bosnia and saw herself as Serbia’s protector.

 

As a result of the Balkan Wars (1912 - 1913), Serbia had doubled in size and there were growing demands for the union of South Slavs (Yugoslavism) under the leadership of Serbia. Austria had a large south Slav population in the provinces of Slovenia, Croatia, the Banat and Bosnia. Austria was very alarmed at the growing power of Serbia. She felt Serbia could weaken her own Empire.

The Austrians decided that they would have to wage a preventative war against Serbia in order to destroy her growing power. They were waiting for the correct pretext (excuse).When Franz Ferdinand was shot the Austrians saw this as the perfect opportunity to destroy Serbia. But when she attacked Serbia, Russia came to her aid and the war spread.

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Bulgaria also became a revanchist, weakened state who seeked to reconquer their lost lands in Serbia, Greece and Romania.