<P> The exact date of the war's end is also not universally agreed upon . It was generally accepted at the time that the war ended with the armistice of 14 August 1945 (V-J Day), rather than the formal surrender of Japan, which was on 2 September 1945 . A peace treaty with Japan was signed in 1951 . A treaty regarding Germany's future allowed the reunification of East and West Germany to take place in 1990 and resolved other post-World War II issues . </P> <P> World War I had radically altered the political European map, with the defeat of the Central Powers--including Austria - Hungary, Germany, Bulgaria and the Ottoman Empire--and the 1917 Bolshevik seizure of power in Russia, which eventually led to the founding of the Soviet Union . Meanwhile, the victorious Allies of World War I, such as France, Belgium, Italy, Romania and Greece, gained territory, and new nation - states were created out of the collapse of Austria - Hungary and the Ottoman and Russian Empires . </P> <P> To prevent a future world war, the League of Nations was created during the 1919 Paris Peace Conference . The organisation's primary goals were to prevent armed conflict through collective security, military and naval disarmament, and settling international disputes through peaceful negotiations and arbitration . </P> <P> Despite strong pacifist sentiment after World War I, its aftermath still caused irredentist and revanchist nationalism in several European states . These sentiments were especially marked in Germany because of the significant territorial, colonial, and financial losses incurred by the Treaty of Versailles . Under the treaty, Germany lost around 13 percent of its home territory and all of its overseas possessions, while German annexation of other states was prohibited, reparations were imposed, and limits were placed on the size and capability of the country's armed forces . </P>

When did first and second world war start