The Most Important Historical Events of the 20th Century

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Updated March 15, 2021 141.7K votes 22.0K voters 760.9K views

It's easy to say the world wouldn't be where it is today without the significant events that transpired throughout the 20th century. These important historical events, such as World War II, Sputnik, and the invention of the internet, truly shaped our world and paved the way for the 21st century and beyond. While all these events changed the world, some can be seen as more important than others—but which ones?

Check out the list of 20th century historical events below and vote up the ones you feel are most significant, and vote down any that seem less important. Of course, you can also add any events that aren't already on the list. 

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  • World War II
    1

    World War II

    2,429 votes
    World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945, though related conflicts began earlier. It involved the 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, and directly involved more than 100 million people from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, erasing the distinction between civilian and military resources. Marked by mass deaths of civilians, including the Holocaust and the strategic bombing of industrial and population centres, it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history. The Empire of Japan aimed to dominate Asia and the Pacific and was already at war with the Republic of China in 1937, but 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 the United Kingdom.
  • World War I
    2

    World War I

    1,749 votes
    World War I, also known as the First World War or the Great War, was a global war mostly centered in Europe that began on 28 July 1914 and lasted until 11 November 1918. More than 9 million combatants and 7 million civilians died as a result of the war, a casualty rate exacerbated by the belligerents' technological and industrial sophistication, and tactical stalemate. It was one of the deadliest conflicts in history, paving the way for major political changes, including revolutions in many of the nations involved. The war drew in all the world's economic great powers, which were assembled in two opposing alliances: the Allies and the Central Powers of Germany and Austria-Hungary. Although Italy had also been a member of the Triple Alliance alongside Germany and Austria-Hungary, it did not join the Central Powers, as Austria-Hungary had taken the offensive against the terms of the alliance. These alliances were reorganised and expanded as more nations entered the war: Italy, Japan and the United States joined the Allies, and the Ottoman Empire and Bulgaria the Central Powers.
  • The Holocaust
    3

    The Holocaust

    3,809 votes
    The Holocaust, also known as the Shoah, was a genocide in which approximately six million Jews were killed by the Nazi regime and its collaborators. Some historians use a definition of the Holocaust that includes the additional five million non-Jewish victims of Nazi mass murders, bringing the total to approximately eleven million. Killings took place throughout Nazi Germany and German-occupied territories. From 1941 to 1945, Jews were targeted and methodically murdered in a genocide, one of the largest in history, and part of a broader aggregate of acts of oppression and killings of various ethnic and political groups in Europe by the Nazis. Every arm of Germany's bureaucracy was involved in the logistics of the genocide, turning the Third Reich into "a genocidal state". Non-Jewish victims of broader Nazi crimes include Gypsies, Poles, communists, homosexuals, Soviet POWs, and the mentally and physically disabled. In total, approximately 11 million people were killed, including approximately one million Jewish children. Of the nine million Jews who had resided in Europe before the Holocaust, approximately two-thirds were killed.
  • Invention of the Internet
    4

    Invention of the Internet

    5,350 votes
  • Beginning of Aviation
    5

    Beginning of Aviation

    2,328 votes
  • Atomic bombings of Hiroshima and Nagasaki
    6
    In August 1945, during the final stage of the Second World War, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. The two bombings, which killed at least 129,000 people, remain the only use of nuclear weapons for warfare in history. As the Second World War entered its sixth and final year, the Allies had begun to prepare for, what was anticipated to be, a very costly invasion of the Japanese mainland. This was preceded by an immensely destructive firebombing campaign that obliterated many Japanese cities. The war in Europe had concluded when Nazi Germany signed its instrument of surrender on May 8, 1945, but with the Japanese refusal to accept the Allies' demands for unconditional surrender, the Pacific War dragged on. Together with the United Kingdom and China, the United States called for the unconditional surrender of the Japanese armed forces in the Potsdam Declaration on July 26, 1945; this was buttressed with the threat of "prompt and utter destruction".