Flanders fields. Graves of the soldiers fallen in the First World War. The First World War became a military cataclism to the scale never seen before.

In 1914 the contradictions and controversies among world powers, their rivalry for political influence and control over world markets, brought the outbreak of the First World War, also called the Great War. This war put against each other the Central Powers (Germany and Austro-Hungary) and the Allies (France, Great Britain, Russia, Japan, Italy since 1915, and the USA since 1917). The German Reich in particular was determined to establish itself as the pre-eminent power in Europe. The Germans also pursued challenging the naval superiority of Great Britain. The immediate cause of hostilities was furnished by rampant nationalism, especially in the Austro-Hungarian Empire. On 28 June 1914, Archduke Francis Ferdinand, heir apparent to the Austro-Hungarian throne, was assassinated in Sarajevo by a Serbian anarchist, Gavrilo Princip. One month later Austro-Hungary declared war on Serbia. Other declarations of war followed quickly, and soon every major power in Europe was in the war. On the Western Front, the Germans marched through Belgium, advanced on Paris and approached the English Channel. After the battles of the Marne and Ypres, however, the Germans became stalled. Gruelling trench warfare and the use of poison gas began all along the front, and for the next three years the battle lines remained virtually stationary despite huge casualties at Verdun and in the Somme offensive during 1916, and introduction of new technics to the fights (tanks, aeroplanes). On the Eastern Front, the Central Powers were more successful. The Germans defeated the Russians near Tannenberg and in Galicia. Serbia and Montenegro fell by the end of 1915 and the front was re-established in northern Greece. In the south, the Italian campaigns were inconclusive, though they benefited the Allied cause by keeping large numbers of Austrian troops tied down there. In Turkey the Allies' ambitious Gallipolli Campaign (1915), an attempt to force Turkey out of the war, was a costly failure. In the Middle East Thomas Lawrence stirred Arab revolt against Turkey. The neutrality of the USA had been threatened since 1915, when the British ship Lusitania was sunk. By 1917 unrestricted German submarine warfare had caused the United States to enter the war on the side of the Allies. In 1917 the Russian revolution broke out. In 1918 the new Soviet government signed the Treaty of Brest-Litovsk with the Central Powers. The Germans were stopped just short of Paris in the second battle of the Marne, and an Allied counter-offensive pushed them back. The Turkish and Austro-Hungarian empires, disintegrating from within, surrendered to the Allies, as did Bulgaria. After the revolution erupted in Germany, the armistice was signed on 11 November 1918. The Treaty of Versailles and other treaties, that ended the war, changed the face of Europe and the Middle East. Four great empires - Germany, Austro-Hungary, Russia, and Turkey - had disappeared by the end of the war. Replacing them were governments ranging from monarchies and sheikhdoms through constitutional republics to the socialist state of the USSR. The war itself had been one of the bloodiest in history, without a single decisive battle. A total of 65 million men and women had served in the armies and navies; an estimated 10 million people had been killed and double that number wounded. Such statistics contributed to a general revulsion against war, leading many to put their trust in multinational disarmament pacts and in the newly formed League of Nations. The First World War was believed to be "the war to end all wars". Instead, it brought "the peace to end all peace".