World War II or the Second World War (often abbreviated WWII)
was a global military conflict which involved a majority of the world's
nations, including all of the great powers, organized into two opposing
military alliances: the Allies and the Axis. The war involved the
mobilization of over 100 million military personnel, making it the most
widespread war in history. In a state of "total war", the major
participants placed their complete economic, industrial, and scientific
capabilities at the service of the war effort, erasing the distinction
between civilian and military resources. Over 70 million people, the
majority of them civilians, were killed, making it the deadliest
conflict in human history. The total financial cost of the war is
estimated at about US$1 trillion,[clarify] making it the most expensive
war as well. Estimates for the total casualties of the war vary, but most suggest
that some 60 million people died in the war, including about 20 million
soldiers and 40 million civilians.[178][179][180] Many civilians died
because of disease, starvation, massacres, genocide. The Soviet Union
lost around 27 million people during the war, about half of all World War II casualties.[181] Of the total deaths in World War II,
approximately 85 percent were on the Allied side (mostly Soviet and
Chinese) and 15 percent on the Axis side. One estimate is that 12
million civilians died in Nazi concentration camps,[182] 1.5 million by
bombs, 7 million in Europe from other causes, and 7.5 million in China
from other causes.[183] Figures on the amount of total casualties vary
to a wide extent because the majority of deaths were not documented.