As President Biden travels to Brussels for an emergency NATOsummit, The Circus examines Russia's threats of using nuclearweapons. Jennifer Palmieri speaks to Pentagon Press SecretaryJohn Kirby about the U.S. response to Putin's nuclearsaber-rattling; John Heilemann games out war simulations withone of the world's foremost experts on nuclear weapons, ZiaMian; and Alex Wagner assesses Putin's motives with formerRussian Foreign Minister Andrei Kozyrev.
