(i) Austria regarded the murder of ArchDuke Franz Ferdinand in Serbia as provocation for war and she decided to retaliate. This forced her Triple Alliance partners Germany and Italy to support Austria, while other powers, Britain, France and Russia came on the opposite side.
(ii) Germany sent troops towards France and seemed to be succeeding, when Russia attacked Germany and Austria from the east. The war became long drawn and more complicated.
(iii) Fighting in the trenches on the ground continued for four years as both sides were evenly matched. Labour from colonies was used for digging trenches. Then the war spread to areas in Asia and Africa.
(iv) Use of technology during the war meant heavy casualties for all countries. For example, on the first day of the Battle of the Somme, 60,000 British soldiers were killed or wounded.
(v) Italy changed sides during the course of the war.
(vi) In April 1917 the US also declared war on Germany.
(vii) The decisive element at this stage was the revolutionary movement in the Russian Empire.
(viii) In October 1917 the Russian Revolution was successful and Russia came out of the war when communists emerged in leadership there. They signed a peace treaty with Germany in March 1918. This treaty was very harsh on Russia, but the new regime in Russia, led by Lenin, agreed to it because they had been opposed to the war from the beginning.
(ix) This complicated matters: not only to Germany, but also to Britain and France, the new Russia seemed a bigger enemy because they were fundamentally opposed to communism.
(x) Therefore, when the fortunes of battle began to turn by the beginning of 1918 and the German armies began to retreat, Britain and France agreed to a peace.
(xi) In Germany too, as in Russia, the workers threatened revolution. Armistice came into effect on November 11, 1918, and then all the powers together put their strength into trying to defeat the revolution in Russia.
