Wars, not just individual or tribal violence, requires heirarical
   societies able to support a significant warrior class. This, in turn,
   requires stores of food significantly in excess of the needs of the
   population. Today, those food stores are only practical to acquire
   through agricultural.  If agricultural were no longer available then
   wars, as we know them, would likely become impractical.
   [1]http://www.shtfplan.com/headline-news/the-next-generation-of-warfare
   -genetically-engineered-viruses_11012018

References

   1. http://www.shtfplan.com/headline-news/the-next-generation-of-warfare-genetically-engineered-viruses_11012018