Why were tensions high in europe in 1914

The event that was widely acknowledged to have sparked the outbreak of World War I occurred on June 28, 1914, when Archduke Franz Ferdinand, heir to the Austro-Hungarian Empire, was shot to death with his wife by the Bosnian Serb nationalist Gavrilo Princip in Sarajevo.By 1914, Austria wanted to crush Serbia. ... Therefore, we can say that Nationalism was an important cause that led to war because it increased tension between great powers such as Russia and Austria – Hungary and led to conflict's that added to Europe's general tension.