Russian President Vladimir Putin on Tuesday signed a revised nuclear doctrine declaring that a conventional attack on Russia by any nation that is supported by a nuclear power will be considered a joint attack on his country.

Putin lowered the bar for a nuclear attack after the US lifted a ban on Ukraine using long-range missiles. Ukraine carried out its first strike with the weapons.

Russian President Vladimir Putin on Tuesday lowered the threshold for nuclear weapons use, just two days after the U.S. authorized Ukraine to use long-range missiles inside of Russia. Putin