Trump’s threats of using nuclear weapons in Afghanistan (recently) and North Korea and elsewhere are not merely his own psychologically distorted fantasies.
Trump’s threats also reflect several decades of official thinking and planning in the Pentagon – and the purposes of some of the new nuclear weapons that the U.S. has been building for several decades.
Just recently the Joint Chiefs of Staff wrote this in a formal document: “Using nuclear weapons could create conditions for decisive results and the restoration of strategic stability. Specifically, the use of a nuclear weapon will fundamentally change the scope of a battle and create conditions that affect how commanders will prevail in conflict.”
See more in this article: https://beyondnuclearinternational.org/2019/08/04/a-winnable-nuclear-war/