If you are refering to the World War I: Following the outbreak of the German Revolution, a republic was proclaimed on 9 November. The Kaiser fled to the Netherlands. On 11 November an armistice with Germany was signed in a railroad carriage at Compiègne. At 11 a.m. on 11 November 1918 — the eleventh hour of the eleventh day of the eleventh month — a ceasefire came into effect. Opposing armies on the Western Front began to withdraw from their positions. Canadian Private George Lawrence Price is traditionally regarded as the last soldier killed in the Great War: he was shot by a German sniper at 10:57 and died at 10:58.
A formal state of war between the two sides persisted for another seven months, until signing of the Treaty of Versailles with Germany on 28 June 1919. Later treaties with Austria, Hungary, Bulgaria and the Ottoman Empire were signed. However, the latter treaty with the Ottoman Empire was followed by strife (the Turkish Independence War) and a final peace treaty was signed between the Allied Powers and the country that would shortly become the Republic of Turkey, at Lausanne on 24 July 1923.
Some war memorials date the end of the war as being when the Versailles treaty was signed in 1919; by contrast, most commemorations of the war's end concentrate on the armistice of 11 November 1918. Legally the last formal peace treaties were not signed until the Treaty of Lausanne. Under its terms, the Allied forces abandoned Constantinople on 23 August 1923.
If you are referig to the Word War II: On July 11 1945, the Allied leaders met in Potsdam, Germany. They confirmed earlier agreements about Germany, and reiterated the demand for unconditional surrender by Japan, specifically stating that "the alternative for Japan is prompt and utter destruction". During this conference the United Kingdom held its general election and Clement Attlee replaced Churchill as Prime Minister.
When Japan continued to reject the Potsdam terms, the United States then dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in early August. Between the two bombs, the Soviets invaded Japanese-held Manchuria, as agreed at Yalta. On August 15, 1945 Japan surrendered, ending the war.