World War One ended at 11am on the eleventh day of the eleventh month, in 1918. Germany signed an armistice (an agreement for peace and no more fighting) that had been prepared by Britain and France. At the start of 1918, Germany was in a strong position and expected to win the war. Russia had already left the year before which made Germany even stronger.
Germany launched the 'Michael Offensive' in March 1918, where they pushed Britain far back across the old Somme battlefield. However, their plan for a quick victory failed when Britain and France counter attacked. Germany and her allies realised it was no longer possible to win the war. The Triple Alliance had been damaged.
Some reasons for this included the fact that the Schlieffen Plan had failed in 1914 and the Verdun Offensive had failed in 1916. Germany was now losing the Great Battle in France and the German Navy had gone on strike and refused to carry on fighting. Furthermore, the United States joined the war in April 1917, which gave the Triple Entente greater power.
Germany was not strong enough to continue fighting, especially as the USA had joined the war and hundreds of thousands of fresh American soldiers were arriving in France. This added greater military strength to the Triple Entente forces. The leaders of the German army told the German government to end the fighting. Kaiser Wilhelm, Germany's leader, abdicated (left his job) on 9 November 1918.
Two days later, Germany signed the armistice and the guns fell silent. People in Britain, France and all of the countries that supported them, celebrated the end of war - a war that had lasted four years and four months. In London, a huge crowd gathered in Trafalgar Square to celebrate the end of the Great War.