What caused World War 1? Alliances, empires and a spark

What caused World War 1 was a local crisis that Europe's great powers chose to escalate. On 28 June 1914, a Bosnian Serb student shot Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, in Sarajevo. Austria-Hungary used the murder to crush Serbia, Germany backed it, Russia backed Serbia, and a web of alliances and war plans pulled in France and Britain. Within 37 days, a Balkan quarrel had become a European war.

In short

• The long-term causes are often summed up as MAIN: militarism, alliances, imperialism and nationalism.
• The short-term cause was the July Crisis of 1914, a chain of decisions in Vienna, Berlin, St Petersburg, Paris and London after the assassination.
• Who was most to blame is still debated: Germany's leaders above all, or a shared failure in which no government wanted a world war but several were willing to risk one.

What were the long-term causes?

By 1914, Europe was split into two armed camps. The usual summary is MAIN, a teaching device rather than a theory, but a useful map of the pressures.

• Militarism. The great powers built huge conscript armies and planned to mobilize them by railway timetable. Germany and Britain ran a naval arms race after 1898, and from 1906 both raced to build the new battleships called dreadnoughts. Generals everywhere believed that whoever struck first would win.
• Alliances. Germany, Austria-Hungary and Italy formed the Triple Alliance in 1882. France and Russia allied in 1894. Britain settled its colonial disputes with France in 1904 and with Russia in 1907, forming a looser Triple Entente. Britain had also, since 1839, guaranteed Belgium's neutrality.
• Imperialism. The powers competed for colonies and influence, and clashed over Morocco in 1905 and 1911. In the Balkans, the decline of the Ottoman Empire left a power vacuum that Austria-Hungary and Russia both wanted to fill.
• Nationalism. Serbia, which had doubled its territory in the Balkan Wars of 1912 and 1913, wanted to unite the South Slavs, including those inside Austria-Hungary. To Vienna, which ruled a dozen peoples, Serbian nationalism was a threat to the empire's survival. Austria-Hungary had annexed Bosnia in 1908, angering Serbia and Russia.

None of these made war inevitable. Europe had come through several crises between 1905 and 1913 without a general war. What the long-term causes did was make the next crisis more dangerous: each government feared that backing down would cost it an ally or its standing as a great power.

What happened in Sarajevo?

Franz Ferdinand visited Sarajevo, the capital of Bosnia, on 28 June 1914. Seven young conspirators were waiting along his route. One threw a bomb that missed the archduke's car. Later that morning, after a wrong turn, his driver stopped close to Gavrilo Princip, 19, who shot and killed the archduke and his wife Sophie.

Princip belonged to a Bosnian nationalist movement, Young Bosnia. The conspirators had been armed and helped across the border by the Black Hand, a secret society of Serbian army officers led by the head of Serbian military intelligence. Whether the Serbian government knew of the plot is still debated, but Vienna was sure Serbia was behind it, and saw the chance to settle accounts.

How did a murder become a world war in five weeks?

The July Crisis moved in steps, and at each one a government could have stopped. The dates below come from the Western Front Association's account of the crisis and the documents themselves.

Date, 1914	Step	Day after the assassination
28 June	Franz Ferdinand assassinated in Sarajevo	0
5 and 6 July	Germany promises Austria-Hungary its full support, the "blank cheque"	7
23 July	Austria-Hungary sends Serbia an ultimatum with a 48-hour deadline	25
25 July	Serbia accepts most demands but not Austrian officials joining the inquiry on its soil	27
28 July	Austria-Hungary declares war on Serbia	30
30 July	Russia orders general mobilization	32
1 August	Germany declares war on Russia	34
3 August	Germany declares war on France	36
4 August	Germany invades Belgium; Britain declares war at 11 p.m. London time	37

The ultimatum was written to be refused. Point 6 demanded that Austro-Hungarian officials "take part in the proceedings" of a Serbian investigation, which no independent state could easily accept. When Serbia's reply, conciliatory but not total, arrived, Vienna broke off relations anyway.

Then the war plans took over. Russia could not mobilize against Austria-Hungary alone without leaving itself exposed to Germany, so it mobilized fully. Germany's only war plan, based on ideas of the former chief of staff Alfred von Schlieffen, assumed a war on two fronts: defeat France fast by marching through Belgium, then turn east before Russia's slower army was ready. That plan meant Russian mobilization turned at once into a German attack on France, through a country Britain had promised to protect. The alliances didn't drag the powers into war automatically; the timetables left almost no time to think.

Who joined, and what did it cost?

The Ottoman Empire entered on Germany's side in late 1914, and Bulgaria in 1915. Japan joined the Entente in August 1914, Italy, abandoning its old allies, in May 1915, and the United States in April 1917. The fighting spread to the Middle East, Africa and the Pacific, which is what made it a world war.

By the armistice of 11 November 1918, the war had cost the lives of more than ten million soldiers, according to the National Army Museum, and millions of civilians through hunger, disease and massacre; estimates of civilian deaths vary widely. Four empires fell: the German, Austro-Hungarian, Russian and Ottoman. In Russia, the war led to the revolutions of 1917 and, in time, the Soviet Union.

Who was to blame?

The winners answered that question in the peace treaty. Article 231 of the Treaty of Versailles, the "war guilt clause", made Germany accept responsibility for all the loss and damage the Allies suffered "as a consequence of the war imposed upon them by the aggression of Germany and her allies". Germans bitterly rejected it, and the resentment helped the rise of Hitler and the road to World War II. Historians have argued over it ever since.

Still argued

Position	Main advocates	The argument
Germany chiefly responsible	Fritz Fischer, Germany's Aims in the First World War (1961 in German)	Germany's leaders wanted a war for European dominance and used the crisis to start it
Shared responsibility	Christopher Clark, The Sleepwalkers (2012)	Every power made choices that led to war; none fully saw where they were heading
Russia and France share more blame	Sean McMeekin, The Russian Origins of the First World War (2011)	Russia's early mobilization and French encouragement turned a local war general
Austria-Hungary and Germany together	Many historians, including Margaret MacMillan, The War That Ended Peace (2013)	Vienna chose war with Serbia, Berlin backed it knowing the risk, others failed to stop it

Many historians still place the heaviest responsibility on Austria-Hungary and Germany for turning the crisis into war, while disagreeing about how far Germany planned it and how much the other powers share; Clark and McMeekin are the best-known dissenters.

Questions like this are why history is argued from evidence rather than settled by treaty: the documents of July 1914 have been read for more than a century, and each generation asks them new questions.

Check yourself

• What does MAIN stand for, and why do historians say none of it made war inevitable?
• Walk through the July Crisis from the assassination to Britain's declaration of war.
• Why did Russian mobilization lead to a German attack on France and Belgium?

Sources

• The July crisis, 1914: what went wrong, 19 steps to disaster — Alan Paton, Western Front Association, 2014
• The Austro-Hungarian Ultimatum to Serbia, English translation — The World War I Document Archive, Brigham Young University Library
• Treaty of Versailles, Part VIII: Reparation — The Avalon Project, Yale Law School
• First World War — National Army Museum