What was considered a short-term cause of World War I?

One of the short-term causes of World War I is commonly attributed to the assassination of Archduke Franz Ferdinand of Austria-Hungary. On June 28, 1914, Gavrilo Princip, a Bosnian Serb nationalist, assassinated the Archduke and his wife during their visit to Sarajevo. This event triggered a series of diplomatic clashes between the major European powers, which were already divided into two rival camps: the Triple Entente (comprising France, Russia, and Britain) and the Triple Alliance (comprising Germany, Austria-Hungary, and Italy).

Austria-Hungary's response to the assassination was to issue an ultimatum to Serbia, which contained demands that were almost impossible to meet. When Serbia did not agree to all the demands, Austria-Hungary declared war on July 28, 1914. This prompted Russia to mobilize in defense of Serbia. Then Germany, an ally of Austria-Hungary, declared war on Russia in support of its ally, setting off a chain reaction of war declarations. Thus, the assassination acted as a catalyst for escalating tensions and pre-existing alliances that led to the outbreak of the war.