Paul Baran and the Origins of the Internet
A looming concern was that neither the long-distance telephone plant, nor the basic military command and control network would survive a nuclear attack. Although most of the links would be undamaged, the centralized switching facilities would be destroyed by enemy weapons. Consequently, Baran conceived a system that had no centralized switches and could operate even if many of its links and switching nodes had been destroyed.
https://www.rand.org/about/history/baran.html
HN discussion: https://news.ycombinator.com/item?id=25544113