War is a state of armed conflict between societies. It is generally characterized by extreme aggression, destruction, and mortality, using regular or irregular military forces. An absence of war is usually called "peace". Warfare refers to the common activities and characteristics of types of war, or of wars in general. Total war is warfare that is not restricted to purely legitimate military targets, and can result in massive civilian or other non-combatant suffering and casualties. 

While some scholars see war as a universal and ancestral aspect of human nature, others argue it is a result of specific socio-cultural or ecological circumstances. 

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 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. In 2003, Richard Smalley identified war as the sixth (of ten) biggest problem facing humanity for the next fifty years. 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. For instance, of the nine million people who were on the territory of Soviet Belarus in 1941, some 1.6 million were killed by the Germans in actions away from battlefields, including about 700,000 prisoners of war, 500,000 Jews, and 320,000 people counted as partisans (the vast majority of whom were unarmed civilians). Another byproduct of some wars is the prevalence of propaganda by some or all parties in the conflict, and increased revenues by weapons manufacturers.
what is the deadliest war in history?
how many died?
over what time period?
how many belarussians were killed by germans away from the battlefield?
what is the second deadliest war in history?
how many deaths did that result in?
do some scholars see war as a part of human nature?
what do other argue it is a result of?
what is war
what is warfare?
what is the opposite of war?
how is total war defined?
how is war characterized?
what do some consider the most destructive war in modern history?
who identified war as the 6th greatest problem facing humanity?
in what year did he say that?
over what time period does he expect humanity to face the problem?
is war good for the ecosystem?
does it increase social spending?
does it create famine?
the Second World War
The deadliest war in history, in terms of the cumulative number of deaths since its start, is the Second World War
60–85 million
Second World War, from 1939 to 1945, with 60–85 million deaths
from 1939 to 1945
Second World War, from 1939 to 1945
unknown
unknown
the Mongol conquests
followed by the Mongol conquests
up to 60 million
he Mongol conquests at up to 60 million
Yes
some scholars see war as a universal and ancestral aspect of human nature
specific socio-cultural or ecological circumstances.
others argue it is a result of specific socio-cultural or ecological circumstances. 
a state of armed conflict between societies
War is a state of armed conflict between societies
the common activities and characteristics of types of war
Warfare refers to the common activities and characteristics of types of war
peace
An absence of war is usually called "peace"
warfare that is not restricted to purely legitimate military targets
Total war is warfare that is not restricted to purely legitimate military targets
by extreme aggression
It is generally characterized by extreme aggression
the Paraguayan War
the most destructive war in modern history may have been the Paraguayan War
Richard Smalley
Richard Smalley identified war as the sixth (of ten) biggest problem facing humanity
2003,
 In 2003, Richard Smalley
the next fifty years
Richard Smalley identified war as the sixth (of ten) biggest problem facing humanity for the next fifty years
No
War usually results in significant deterioration of infrastructure and the ecosystem
No
War usually results in significant deterioration of infrastructure and the ecosystem, a decrease in social spending
Yes
War usually results in significant deterioration of infrastructure and the ecosystem, a decrease in social spending, famine