War is a state of armed conflict between societies.

The deadliest war in history, in terms of the cumulative number of deaths since its start, is the Second World War, from 1939 to 1945, with 60–85 million deaths, followed by the Mongol conquests[4] at up to 60 million. As concerns a belligerent's losses in proportion to its prewar population, the most destructive war in modern history may have been the Paraguayan War (see Paraguayan War casualties). In 2013 war resulted in 31,000 deaths, down from 72,000 deaths in 1990.[5] In 2003, Richard Smalley identified war as the sixth (of ten) biggest problem facing humanity for the next fifty years.[6] War usually results in significant deterioration of infrastructure and the ecosystem, a decrease in social spending, famine, large-scale emigration from the war zone, and often the mistreatment of prisoners of war or civilians.[7][8][9] For instance, of the nine million people who were on the territory of Soviet Belarus in 1941