Bulgaria was a province of the Ottoman Empire from the 14th century until support from Russia enabled it to become an autonomous principality in 1878. Revolution in Turkey in 1908 undermined the power of Abdul Hamid II and enabled Bulgaria to become an independent kingdom under Prince Ferdinand.

Bulgaria's parliament was elected by manhood suffrage and had the power to veto royal legislation. The most powerful political group in parliament was the Nationalist Party. In 1913 Vasil Radoslavov became Bulgaria's prime minister.

Prince Ferdinand favoured an expansionist foreign policy and during the Balkan Wars joined with Serbia, Greece and Montenegro to drive Turkey out of Macedonia. In 1913 Prince Ferdinand launched an attack on its former allies. Bulgaria was defeated in six weeks and as a result lost Bulgarian-speaking parts of Macedonia and the coastal region of Dobrudja.

In 1910 the Bulgarian Army comprised some 85,000 troops in peacetime. All men aged between 20 and 46 could be called up during a war. After the Balkan Wars (1912-13) the size of the army was increased to ten divisions. Each division of 24,000 men were supported by cavalry squadrons, machine-gun troops and field artillery.