Russia's nuclear threat explained

Russian President Vladimir Putin conjured the specter of nuclear war during the last week's fierce fighting in Ukraine, instructing Russia's military to place nuclear forces on "high combat alert," a "special regime of combat duty."

When was the last time there was a nuclear alert like this?

The last nuclear alert in a U.S.-Russian/Soviet crisis was by the United States during the 1973 Yom Kippur war, according to James Acton, who co-directs the Nuclear Policy Program at the Carnegie Endowment for International Peace. Before that, many experts say the closest the Cold War powers came to nuclear war was the Cuban missile crisis in 1962.

Acton wrote an instructive Twitter thread about Russia's current nuclear threat.

He explains that Russian nonstrategic warheads are stored separately from the weapons that carry them,