Certainly the assassination of Archduke Franz Ferdinand on June 28, 1914 in Sarajevo, Bosnia gave Austria-Hungary an excuse to declare war on Serbia (sec.7 The Assassination of the Archduke). Austria-Hungary had no knowledge as to whether Gavrilo Princip was instructed to assassinate Franz Ferdinand by the Serbian government or if he was a radical vigilante. If the assassination had been the work of the Serbian government, Austria-Hungary was not going to let Serbia get away with murder, especially due to the fact Franz Ferdinand was visiting Sarajevo peacefully. Austria-Hungary sent an ultimatum to Serbia on the same day as Franz Ferdinand’s death demanding all media and organizations against Austria-Hungary to be shut down, all military officials guilty of anti-Austro-Hungarian propaganda to be discharged and for all citizens loosely involved in the assassination conspiracy to be investigated by the Austro-Hungarian judicial system. Serbia did not cooperate, an action Austria-Hungary took as an invitation to go to war. It was only after Austria-Hungary and Serbia went to war that other countries begin a domino effect into battle. No two major European powers had gone to war since the Franco-Prussian War of 1870, so the likelihood of a such a widespread outbreak of violence was low. A change in this condition could be achieved only if two countries reached a breaking point in their deep-rooted tensions relating to military and imperial power, or in special circumstances which Ferdinand’s assassination provided. With that being said, it is important to acknowledge that the assassination was an immediate major conflict between Austria-Hungary and Serbia, but the two countries had long-standing imperial conflicts (sec.6 Nationalism in the Balkans sub sec.2).
Only a week after Austria-Hungary went to war with Serbia, all other strong European powers were immersed into battles of their own (sec.9 The Alliance System Leads to War). Russia was afraid of Austria-Hungary succeeding in an annex of the Balkan Peninsula so they took it as an obligation to mobilize their army towards Austro-Hungarian and German lines (sec.9 The Alliance System Leads to War). Other nations began mobilization due to the fact they were all tied into “a web of interlocking treaties - known as the system of alliances” (sec.5 The System of Alliances). Austria-Hungary, Germany, and Italy became known as the Triple Alliance, while France, Great Britain, and Russia formed the Triple Entente. Competition between the nations listed above was intensified once the alliances were born as it created one intense rivalry. Hypothetically speaking, if Great Britain were to attack Italy, Austria-Hungary and Germany would then attack Great Britain. Next, France and Russia would