Though there are many factors that contributed to their outbreak of World War I, tensions within the Balkans can be said to be the biggest reason the second largest war in history was erupted. Strong national tensions in the Balkans eventually led Serbian terrorists to assassinate Fransduke Ferdinand, Austria's heir to the throne, which let loose the entire war by causing alliances on the sides of either Serbia or Austria to fight each other and drag the US into the war. .
The Balkans were a focal point for European power because of their territory and resources. They did even not receive the chance to be independent until the Ottoman Empire declined in the early 20th century, yet even then they were still mostly controlled by the Turks. Watching other countries around them unite fired greater desire to become independent, leading the Balkans to revolt in 1875 with the aid of Russia. However, they could not obtain complete freedom for Turkey, as parts of the Balkans were still controlled by them. .
Ten years later, Eastern Rumelia revolted against Turkish rule with the aid of Bulgaria, winning the Battle of Slivnitza, and later adding Britain to their alliance. Crete religious tensions in 1879 caused numerous Muslims and Christians to be murdered, which caused Greece to get involved in aiding another attack on Turkey, who lost their own homeland in the end. By 1912 the Balkan League was formed, who was still intent of ridding their county of the loathed Serbs. They were successful in the Balkan Wars, which threatened other great powers. With the decline of Bulgaria and Turkey in the Balkans, the Serbs were able to gain a great deal of power and wanted to unite all Slavs in the area. They wished to gain the Slavs of Bosnia, but the country was owned by Austria-Hungary at the time. Angered, Serbian nationalists assassinated Archduke Francis Ferdinand, heir to the Austrian throne, and lit the spark that set off World War I.