Russia warns of World War III if Ukraine joins NATO

What would happen if a nuclear war were to be sparked between Russia and the United States today? Who would survive?
In our most scientifically realistic simulation to date, we show what a nuclear war between Russia and the United States might look like today. It is based on detailed modeling of nuclear targets, missile trajectories, and the effects of blasts, EMPs, and smoke on the climate and food resources.
U.S. Army unclassified report AD-A178230 (1994)
Blast modeling:
Prof. Alex Wellerstein, Stevens Inst. of Technology, https:/www.nukemap.org