While experts, commentators, and many others have been urging Washington to discount or even ignore Putin’s threats, U.S. President Joe Biden and his team know better. Claims that Ukraine lacks good targets, Russian bombs might not work, Putin’s officers could refuse to execute orders, or the risk of radiation spreading into Russia would be unacceptable are dangerous wishful thinking. Biden, CIA Director William Burns, and U.S. National Security Advisor Jake Sullivan have concluded that Putin is deadly serious. As Sullivan acknowledged last September, “We have communicated directly, privately, at very high levels to the Kremlin that any use of nuclear weapons will be met with catastrophic consequences for Russia.”
Allison, Graham. "Nuclear Weapons Still Matter." Foreign Policy, January 5, 2023.