On 28 June 1914, Austrian Archduke Franz Ferdinand visited the Bosnian capital, Sarajevo. A group of six assassins (Cvjetko Popović, Gavrilo Princip, Muhamed Mehmedbašić, Nedeljko Čabrinović, Trifko Grabež, Vaso Čubrilović) from the nationalist group Mlada Bosna, and supplied by the Black Hand, had gathered on the street where the Archduke’s motorcade would pass. Čabrinović threw a grenade at the car, but missed. It injured some people nearby, and Franz Ferdinand’s convoy carried on. The other assassins failed to act as the cars drove past them. About an hour later, when Franz Ferdinand was returning from a visit at the Sarajevo Hospital with those wounded in the assassination attempt, the convoy took a wrong turn into a street where, by coincidence, Princip stood. With a pistol, Princip shot and killed Franz Ferdinand and his wife Sophie. The reaction among the people in Austria was mild, almost indifferent. As historian Zbyněk Zeman later wrote, “the event almost failed to make any impression whatsoever. On Sunday and Monday [June 28 and 29], the crowds in Vienna listened to music and drank wine, as if nothing had happened.”
Escalation of violence in Bosnia and Herzegovina
However, in Sarajevo itself, Austrian authorities encouraged violence against the Serb residents, which resulted in the Anti-Serb riots of Sarajevo, in which Croats and Bosnian Muslims killed two ethnic Serbs and damaged numerous Serb-owned buildings. The events have been described as having the characteristics of a pogrom. Writer Ivo Andrić referred to the violence as the “Sarajevo frenzy of hate.” Violent actions against ethnic Serbs were organized not only in Sarajevo, but also in many other large Austro-Hungarian cities in modern-day Croatia and Bosnia and Herzegovina. Austro-Hungarian authorities in Bosnia and Herzegovina imprisoned and extradited approximately 5,500 prominent Serbs, 700 to 2,200 of whom died in prison. 460 Serbs were sentenced to death and a predominantly Muslim special militia known as the Schutzkorps was established and carried out the persecution of Serbs.
The assassination led to a month of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France, and Britain called the July Crisis. Believing correctly that Serbian officials (especially the officers of the Black Hand) were involved in the plot to murder the Archduke, and wanting to finally end Serbian interference in Bosnia, Austria-Hungary delivered to Serbia on 23 July the July Ultimatum, a series of ten demands that were intentionally made unacceptable to provoke a war with Serbia. The next day, after the Council of Ministers was held under the chairmanship of the Tsar at Krasnoe Selo, Russia ordered general mobilization for Odessa, Kiev, Kazan and Moscow military districts and fleets of the Baltic and the Black Sea. They also asked for other regions to accelerate preparations for general mobilization. Serbia decreed general mobilization on the 25th and at night, declared that they accept all the terms of the ultimatum, except the one claiming that Austrian investigators visit the country. Following this, Austria broke off diplomatic relations with Serbia, and the next day ordered a partial mobilization against Serbia. Finally, on July 28, 1914, Austria-Hungary declared war on Serbia.
On 29 July, Russia, unwilling to allow Austria-Hungary to eliminate its influence in the Balkans, and in support of its longtime Serb protégé, unilaterally declared – outside of the conciliation procedure provided by the Franco-Russian military agreements – partial mobilization against Austria-Hungary. German Chancellor Bethmann-Hollweg was then allowed until the 31st for an appropriate response. On the 30th, Russia ordered general mobilization against Germany. In response, the following day, Germany declared a “state of danger of war.” This also led to the general mobilization in Austria-Hungary on August 4. Kaiser Wilhelm II asked his cousin, Tsar Nicolas II, to suspend the Russian general mobilization. When he refused, Germany issued an ultimatum demanding the arrest of its mobilization and commitment not to support Serbia. Another was sent to France, asking her not to support Russia if it were to come to the defense of Serbia. On August 1, after the Russian response, Germany mobilized and declared war on Russia.
The German government issued demands that France remain neutral as they had to decide which deployment plan to implement, it being difficult if not impossible to change the deployment part-way through it. The modified German Schlieffen Plan, Aufmarsch II West, would deploy 80% of the army in the west, and Aufmarsch I Ost and Aufmarsch II Ost would deploy 60% in the west and 40% in the east as this was the maximum that East Prussia’s railway infrastructure could support. The French did not respond but sent a mixed message by ordering their troops to withdraw 10 km (6 mi) from the border to avoid any incidents while ordering the mobilisation of her reserves. Germany responded by mobilising its own reserves and implementing Aufmarsch II West. Germany attacked Luxembourg on 2 August and on 3 August declared war on France. On 4 August, after Belgium refused to permit German troops to cross its borders into France, Germany declared war on Belgium as well. Britain declared war on Germany at 7 pm UTC on 4 August 1914 (effective from 11 pm), following an “unsatisfactory reply” to the British ultimatum that Belgium must be kept neutral.