Putin is the primary decision-maker on the use of Russia's nuclear arsenal. The doctrine said any attack by a non-nuclear power supported by a nuclear power would be considered a joint attack, and that any attack by one member of a military bloc would be considered an attack by the entire alliance, it said.

Russian President Vladimir Putin formally lowered the threshold for his country's use of nuclear weapons Tuesday, after the U.S. allowed Ukraine to strike inside Russia using American missiles.

Russia is again threatening the use of nuclear weapons against Ukraine, as the country lowers its own threshold for when it might use those kinds of weapons.

President Vladimir Putin has approved changes to Russia’s nuclear weapons policy, and Moscow has urged the West to study them closely. Putin signed a decree on Tuesday updating Russia’s nuclear doctrine,