An in-depth report in  The Diplomat of 9 August by Masashi Murano, research Fellow at the Okazaki Institute (Tokyo).  This show that in response to advanced nuclear threats from Russia, and highly-developed anti-access and area denial (A2/AD) capabilities of China and North Korea, the 2018 Nuclear Posture Review (NPR) "commits to maintaining and modernizing the U.S. nuclear triad — intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and strategic bombers — and positioning dual capable aircraft (DCA) that can be deployed globally as an important element in the extended deterrence toolkit."

What apparently hasn't been assessed are risks of resorting to low-yield (0.3 kilotons) nuclear missiles. Although much less devastating than the Hiroshima nuclear bomb (15 kilotons), the nuclear destruction and fall-out can be frightening. Even meant largely as a deterrent, its proliferation and readiness are likely to increase the probability of use. Potential rapid escalations are not amenable to easy control. Any unintended level of escalation due to perceived existential national security could plunge the world into an all-out nuclear war.