Historian Peter Kuznick fears for the fate of humanity ... warning of a third world war and a nuclear winter if conflicts across the globe continue to escalate.
The author and American University professor joined us on "TMZ Live" Thursday, and we asked him just how close we are to World War III, given the war in the Middle East.
Peter says things were already trending towards a doomsday scenario as a result of the war between Ukraine and Russia and the situation in Taiwan ... and he fears recent developments in Gaza may push things over the edge.
The way Peter sees a nightmare situation unfolding -- Israel invades Palestine, forcing Hezbollah to join the war -- and then other countries are drawn into battle.
From there, Peter says it's an all-out world war ... and it's pretty much guaranteed nuclear warheads will be used.
Peter explains how even a small number of nukes would create a nuclear winter capable of killing 2 billion people across the globe ... telling us it would be worse than ever imagined.
With the United States mobilizing warships, aircraft and troops to help Israel, Peter says humanity is sitting on the proverbial powder keg ... but he's got some solutions to avoid cataclysm.