1940s

The 20th century is defined as the time period running from January 1, 1901 to December 31, 2000. The Chinese, Russian, German, Ottoman, and... Austro-Hungarian empires dissolved in the first half of the century, with all but the British, French, and Japanese empires collapsing during the course of World War I, and Russia transformed into communist state of Soviet Union. The inter-war years saw a Great Depression cause a massive disruption to the world economy. Shortly afterwards, World War II broke out, pitting the Allied powers against the Axis powers which eventually resulted in a total victory for the Allies, at the cost of over 60 million lives and the complete devastation of many nations. Remaining colonial empires dissolved shortly after the war. As a means of preventing future world wars, the United Nations was formed; however, competition between the two new superpowers, the Soviet Union and the United States, resulted in the Cold War, which would dominate geopolitical life for the next 45 years.
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World War II, or the Second World War , was a global war that was under way by 1939 and ended in 1945. It involved a vast majority of the... world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, with more than 100 million people serving in military units. In a state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant events involving the mass death of civilians, including the Holocaust and the only use of nuclear weapons in warfare, it resulted in 50 million to over 70 million fatalities. These deaths make the war the deadliest conflict in human history. Although Japan was already at war with China in 1937, the world war is generally said to have begun on 1 September 1939, with the invasion of Poland by Germany, and subsequent declarations of war on Germany by France and most of the countries of the British Empire and Commonwealth.
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