World War III (
WWIII,
WW3 or the
Third World War) is a
hypothetical worldwide military conflict subsequent to
World War II. Because of the development and use of
nuclear weapons near the end of World War II and their subsequent acquisition and deployment by
several countries, it is feared that a third world war could cause the end of
human civilization and most or all
human life on
Earth. A common hypothesis is that a small number of people could survive such an
Armageddon, possibly in deep underground
blast shelters or away from Earth, such as on the
Moon or
Mars or in
space vehicles. Another major concern is that
biological warfare could cause a very large number of casualties, either intentionally or inadvertently by an accidental release of a biological agent, the unexpected mutation of an agent, or its adaptation to other species after use.