A twenty-first-century nuclear war on Earth, fought from 2026 to 2053, in which about six hundred million people died.
World War III was a global conflict on Earth in the twenty-first century, fought from 2026 to 2053. Nuclear weapons were used, many governments collapsed, and in Star Trek: First Contact Data states that about six hundred million people died. One of the war's notorious figures, Colonel Phillip Green, appears as a recreated villain in the original series episode The Savage Curtain.
The years after the war left Earth in ruins. In Encounter at Farpoint, Q puts Picard on trial in a recreation of a post-atomic court from that era, where drugged soldiers enforce rough justice.
In 2063, ten years after the war's end, Zefram Cochrane flew the Phoenix, the first human warp ship, from a former missile silo in Montana. The flight drew the attention of a passing Vulcan ship, and first contact with the Vulcans helped humanity move past the devastation. The Borg tried to stop that flight in First Contact.