USA significantly lowered threshold of nuclear weapons use | Vladimir Kozin, leading expert at the Military-Political Studies Center of the MGIMO | infobrics.org

"Barack Obama's nuclear strategy approved in 2010 had 6 reasons for using nuclear weapons, their number grew to 14 in Donald Trump's relevant strategy approved in 2018.  

There are just two provisions in the section dedicated to the possible use of nuclear weapons in current Russia's military strategy approved in 2014."