Answer:
The world war fourth hasn't happen yet. So far, we have gone through two big wars. The first world war that lasted from 28 July 1914 to 11 November 1918, and the second world war that lasted from 1939 to 1945.
According to conspiracy theories, the fourth World War envisions an attack on Iraq, Iran and/or Syria. Once America is firmly focused on the Middle East, North Korea is to attack South Korea and China is to invade Taiwan.
We really hope this not to happen!