World War I or the
First World War (sometimes written
WW1 or
WWI for short) was a war fought by many countries, which is why it is called a "world" war. It started in 1914 and ended in 1918.
[5] Before
World War II began in 1939, World War I was called the
Great War, the
World War or
the War to End all Wars. 135 countries took part in World War I, and more than 15,000,000 people died in the war.
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