The assassination of Archduke Franz Ferdinand (1863 to 1914) in the Balkans in the summer of 1914 set off a chain of events that led to the First World War (1914 to 18). For over a decade before, imperialistic governments, a fierce arms race, rising nationalism, and the obligations of a complex web of international alliances created an atmosphere that war was very much in the air. When Franz Ferdinand, heir to the Habsburg throne that ruled Austria-Hungary, was shot in Sarajevo on 28 June 1914 by a Serbian nationalist, individual ambition and the obligations of the pre-WWI alliance system resulted in all the major European powers declaring war on each other by the following August.

The Triple Alliance of Germany, Austria-Hungary, and Italy had formed in 1882, and it faced off against the Triple Entente (aka the Allies) of Great Britain, France, and Russia, formed in 1907. The alliance system had already been tested in the two Moroccan Crises of 1905 to 6 and 1911, when Germany tried to muscle in on French dominance in Morocco. Germany had backed down each time, and war, although seeming inevitable, was averted by diplomacy. A third test would come in the Balkans, a hotbed of nationalism and a key area of imperial squabbling, particularly between Austria-Hungary and Russia.

Backing Austria-Hungary was Kaiser Wilhelm II (1859 to 1941), who came to power as emperor of Germany in 1888 (and reigned until 1918). The kaiser was determined to expand Germany's rather small empire and defend Germany against two enemies, France in the west and Russia in the east. The Anglo-German arms race had seen these countries plough enormous sums of money into expanding and improving their naval fleets. Britain could not afford Germany to become too powerful and threaten its global empire. With Russia and Austria-Hungary eager to expand their influence in the Balkans, all that was needed to start a domino effect of alliance obligations kicking in was an international incident in Sarajevo.

The Balkans, a geographical meeting point of empires, had been an area of territorial disputes for many decades. Russia, Austria-Hungary, and the crumbling Ottoman Empire here jostled for control of certain regions. In October 1908, Austria-Hungary, fearing the growing influence of reformists, annexed Bosnia-Herzegovina. The Russian Tsar protested. The German Kaiser made it clear he was prepared to fight to support Austria-Hungary. Serbia was a key player in this ongoing crisis. Here, the ruling monarchy was against interference from the Ottoman and the Austro-Hungarian empires but pro-Russian. The Serbian government even wanted to create a new coalition of Slavic states, and the forerunner of this ambition was the Balkan League, formed in 1912. Russia supported this league, which consisted of Serbia, Bulgaria, Montenegro, and Greece. The Balkan League declared war on the Ottoman Empire in October 1912 and successfully drove the Turks out of the region. This was the First Balkan War, but it ended in bitter disappointment for the Serbians, since Albania and access to the Adriatic Sea were denied to them by the 1913 Treaty of London. Greece and Bulgaria were also frustrated by their lack of significant territorial gains. Perhaps inevitably, a Second Balkan War erupted in June 1913. Bulgaria invaded Serbia, and Greece, Romania, and Turkey then declared war on Bulgaria. Bulgaria lost the war, and the 1913 Treaty of Bucharest reshuffled the Balkan borders once again. Ominously, Serbia, although doubling its territory, still had not gained its wished-for Adriatic port. Serbia was a state with an army of 200,000 men, and it continued to pose a direct threat to Austria-Hungary, which, given its poor military status, was dependent on Germany to protect the status quo.

Franz Joseph I (reign 1848 to 1916) was the ruler of the Austro-Hungarian Empire. He was both Emperor of Austria and King of Hungary. The heir was Franz Joseph's son Rudolph, but he died in 1889, and so the emperor's younger brother, Archduke Karl Ludwig (born 1833), became the next in line to the throne. When Ludwig died in 1896, his son, Franz Ferdinand (born 1863), became the heir apparent. Archduke Franz Ferdinand enjoyed a military career that saw him rise to the rank of field marshal. In his role as Inspector General of the Austro-Hungarian army, Franz Ferdinand decided to tour Bosnia on an inspection of the traditional summer manoeuvres of the Austro-Hungarian armed forces. The Bosnian local government warned the archduke that the visit was ill-timed and hinted that it might even be dangerous.

Bosnia's capital was Sarajevo, a hotbed of local nationalism with several pro-Slavic movements still seething over the 1908 annexation. A Serbian nationalist group, the Black Hand, led by Colonel Dragutin Dimitrijević (nicknamed Apis or 'the Bull'), the head of Serbian military intelligence, was determined to kill Sarajevo's illustrious visitor. The Black Hand was actually the name used by its enemies; the members themselves called their organisation Union or Death in reference to the oath they swore to give everything for the Slavic cause. The Black Hand members ultimately wanted to unite the Serbs in Bosnia with Serbia itself, and they had already made a failed attempt to assassinate Emperor Franz Joseph back in 1911. The group received the support of senior figures from the Serbian military. A group of seven students, who had all been radicalised, trained, and equipped in Serbia by the Black Hand organisation, was tasked with the archduke's assassination. On the morning of Sunday, 28 June, the archduke and his wife, Duchess of Hohenberg, also known as Countess Sophie Chotek, travelled by car from the city's train station to the town hall. The date was a significant one for Serbians, marking their defeat at the Battle of Kosovo to Turkey in 1389, a loss which traditionally marked the beginning of Serbia's long oppression by foreign powers.

The streets of Sarajevo were lined with onlookers as the archduke drove past. In amongst the crowd were the Black Hand assassins. One of the students, Nedeljko Čabrinović, threw a bomb or grenade at the archduke's car, but it bounced off and exploded beneath the car behind. Čabrinović immediately took poison and threw himself into a river, but as neither proved an effective suicide method, he was arrested. The other five Black Hand agents fled the scene, but three were later arrested and confessed to the plot.

The archduke cancelled the rest of his tour of Bosnia, but, after the reception lunch at the town hall, he unwisely decided to again ride through the streets of Sarajevo that afternoon in his open-top car, once more with his wife by his side. The archduke's idea, taking an unplanned route, was to visit the victims of the morning's bomb attack and show that the monarchy would not be daunted by terrorism. The problem was that the driver had not been told of the new route, and so he was obliged to make a U-turn after taking the wrong road. As the car slowed to make the turn, a young Bosnian Serb nationalist, Gavrilo Princip (1894 to 1918), stepped out of the crowd. Princip had been one of the six would-be assassins who had failed that morning, and now he could hardly believe he had been given a second chance. Pulling out his Black Hand pistol, Princip shot both the archduke and his wife. Countess Sophie Chotek died instantly, the archduke ten minutes later. Princip was promptly arrested.

It was revealed that Serbian frontier guards had helped the group of assassins to cross the Serbian border. It seemed, then, there was at least some official Serbian involvement in the plot. Emperor Franz Joseph was understandably outraged at the murder of his heir and particularly angry at the official Serbian connection, no matter how tentative. The Serbian government was promptly blamed for the assassination. The late archduke and his wife were given a state funeral in Vienna on 4 July. Franz Joseph, meanwhile, sought the backing of Germany for his plan to take over Serbia. The emperor was egged on by his gung-ho chief of general staff, General Franz Conrad von Hötzendork (1852 to 1925), who had been calling for a war against Serbia for years. The kaiser gave his support on 6 July in what has been described as a 'blank cheque' freedom of action notice. All this was despite the obvious threat that Russia would not permit a war against Serbia and would likely intervene, which, in turn, might well draw in Britain and France through their treaty obligations. Perhaps the kaiser was intent on war.

International relations deteriorated during the so-called 'July Crisis' of 1914. Russia was intent on protecting Serbian independence, and Tsar Nicholas II (reign 1894 to 1917) gained the backing of the French government. The Austro-Hungarian government, nevertheless, issued an ultimatum to the government of Serbia on 23 July, formally accusing it of involvement in the assassination and requiring the suppression of the nationalist movements within its borders. The Serbian government considered the ultimatum and agreed to further negotiations. Austria-Hungary insisted on the immediate acceptance of the ultimatum's demands.

Both Austria-Hungary and Germany rejected a proposal from Britain to hold a peace conference to discuss the issue. On 28 July, Austria-Hungary formally declared war on Serbia and began to bomb Belgrade. Russia insisted it would go to war if Habsburg troops were not withdrawn from Serbia, and so the tsar sent a telegram to Kaiser Wilhelm, stating "To try and avoid such a calamity as a European war, I beg you in the name of our old friendship to do what you can to stop your allies going too far" (McDonough, 20). Austria-Hungary refused to back down, Russia threatened to mobilise its army, and Germany threatened to do the same in retaliation. Nobody backed down. The tsar mobilised his army on 30 July. The next day, the kaiser demanded Russia's mobilisation end. All parties might still have hoped to keep the crisis local, but on 1 August 1914, Germany declared war on Russia. The same day, both Germany and France mobilised their armies. Italy declared it would remain neutral in the coming conflict, at least for the moment. On 2 August, Germany invaded Luxembourg and Britain mobilised its navy.

The German generals were desperate to avoid a war on two fronts (France and Russia) and so had created the Schlieffen plan as far back as 1905. This plan aimed to swiftly surprise and defeat France by marching through neutral Belgium. This would then allow Germany to concentrate its forces against Russia. Time was of the essence, since the Schlieffen plan had to be put into action before Russia mobilised its much bigger army. Britain informed the German government that it was prepared to defend Belgium's neutrality and support France. On 3 August, German troops marched through Belgium, and Germany formally declared war on France. On 4 August, Britain declared war on Germany. On 6 August, Austria-Hungary declared war on Russia, and Serbia declared war on Germany. On 10 August, France, which had already declared war on Germany, also declared war on Austria-Hungary; Britain followed suit on 12 August. The world was about to endure a conflict the likes of which it had never experienced.

The armies of Austria-Hungary, Germany, and Bulgaria invaded Serbia in October 1915. Austria-Hungary later attacked Montenegro and Albania. The campaign in Serbia was particularly brutal as the assassination had a direct effect on the actions of the Austro-Hungarian army, which was guilty of taking civilian hostages and conducting summary executions. Here, the historian J. Horne explains:

Precisely because it aimed to punish the Serbs collectively for the 'terrorist' assassination of the Archduke Franz-Ferdinand and to destroy Serbia as a nation-state, the Austro-Hungarian military was predisposed to see the entire population as made up of terrorists and bandits…

(Winter, 571).

The Triple Entente powers, who were eventually joined by Italy and the United States, amongst others, won WWI, despite Russia withdrawing after the Bolshevik Revolution of 1917. As the primary losers, the Austro-Hungarian Empire was broken up, and Germany's territories were greatly reduced. Čabrinović and Princip never saw victory; both died in prison, the former in 1916, and the latter in April 1918, six months before the November armistice ended WWI. The Treaty of Versailles, which set out the terms of peace, was signed in 1919, five years to the day after the assassination of Franz Ferdinand.