The name the war soon earned reflects something its own generation already knew: this was not only a European quarrel. Fighting spread across Eastern Europe, the Middle East, Africa, Asia and the oceans, and millions of soldiers and laborers came from colonies on every inhabited continent.

The Eastern Front

In the east, distances were vast and the lines moved much more than in the west. Russia invaded East Prussia in August 1914, sooner than Germany expected, but at Tannenberg in August 1914, German forces under Paul von Hindenburg and Erich Ludendorff destroyed a Russian army, making both generals national heroes. Austria-Hungary fared badly against Russia in Galicia and even against Serbia. In 1916 the Russian general Aleksei Brusilov launched one of the war's most successful offensives against Austria-Hungary, but at enormous cost. Russia's losses helped bring on the revolutions of 1917, covered in Level 6.

The Ottoman fronts

The Ottoman Empire entered the war on Germany's side in late 1914, opening fronts in the Caucasus, in Mesopotamia (modern Iraq), in Sinai and Palestine, and at the Dardanelles, the straits leading to its capital, Constantinople.

In 1915 Britain and France tried to force the straits, knock the Ottomans out and open a supply route to Russia. After a naval attack failed in March, troops landed on the Gallipoli peninsula on 25 April 1915. The ANZACs, soldiers from Australia and New Zealand, are especially remembered for fighting at Gallipoli, alongside British, French, Indian and Newfoundland troops. Ottoman defenders, among them a young officer named Mustafa Kemal, held the heights. After about eight months the Allies withdrew, with roughly half a million casualties on the two sides. Victory at Gallipoli became a founding story of modern Turkey, which Kemal later led as Atatürk, and 25 April is still kept as Anzac Day in Australia and New Zealand.

In Mesopotamia a British and Indian force surrendered to the Ottomans at Kut in April 1916, though Britain went on to take Baghdad in 1917. In 1916 Sharif Hussein of Mecca launched the Arab Revolt against Ottoman rule, encouraged by British promises of Arab independence. Yet in the secret Sykes-Picot Agreement of 1916, Britain and France planned to divide the Ottoman Arab lands between them, and in the Balfour Declaration of November 1917 Britain announced its support for "a national home for the Jewish people" in Palestine. These overlapping promises shaped conflict in the Middle East for the next century.

The Armenian genocide

Under cover of war, the Ottoman government, led by the Committee of Union and Progress, turned on its Armenian Christian subjects, whom it accused of siding with Russia. Beginning in April 1915, Ottoman authorities deported and massacred Armenians, driving columns of women, children and old people on death marches into the Syrian desert. Estimates of the dead range from about 600,000 to more than a million. Assyrian and Greek Christians also suffered mass killing. These events later shaped the thinking of the lawyer Raphael Lemkin, who coined the word genocide. The Republic of Turkey has long rejected the term genocide for these events, a term most historians of the subject accept.

Empires at war

Britain and France drew heavily on their empires. Over a million soldiers from British India served overseas during the war, in France, Mesopotamia, Egypt and East Africa. France recruited hundreds of thousands of colonial soldiers, including West African troops known as tirailleurs sénégalais, along with North African and Indochinese workers. About 140,000 Chinese laborers worked behind the lines for Britain and France, digging trenches, unloading ships and later clearing battlefields. Canada, Australia, New Zealand, South Africa and Newfoundland sent large forces, and many people in those dominions came to see the war as the moment their nations came of age.

In Africa, Allied forces soon took most of Germany's colonies, but in German East Africa (roughly modern Tanzania) the German commander Paul von Lettow-Vorbeck kept up a guerrilla campaign until after the armistice. Both sides depended on African porters, who carried supplies on foot through bush and swamp. Tens of thousands of African carriers died, mostly of disease, hunger and overwork, by some estimates well over a hundred thousand, far more than the soldiers killed in combat there. Japan, allied with Britain, seized German bases in China and the Pacific.

Worked example: a soldier from Punjab

Imagine a young Sikh soldier from Punjab sent to Flanders in the autumn of 1914. He arrives in summer uniform as winter begins, fighting for an empire in which he has no vote, against an enemy he had barely heard of. Indian soldiers' letters home, read by British censors, show pride in their courage alongside fear, homesickness and anger at unequal treatment. When the war ended, many Indians expected political reward. Instead, Britain extended wartime emergency powers, and in April 1919 troops fired on an unarmed crowd at Amritsar, killing hundreds. The story shows how the war's sacrifices and broken promises fed demands for self-rule across the colonial world, a thread taken up in Level 8. It also raises a question of equal worth: what does a state owe the people it asks to die for it?