Putin lowers the threshold for using his nuclear arsenal after Biden's arms decision for Ukraine

President Vladimir Putin on Tuesday formally lowered the threshold for Russia’s use of its nuclear weapons, a move that follows U.S. President Joe Biden’s decision to let Ukraine strike targets inside Russian territory with American-supplied longer-range missiles.

The new doctrine allows for a potential nuclear response by Moscow even to a conventional attack on Russia by any nation that is supported by a nuclear power.

Russia’s Defense Ministry said Ukraine fired six U.S.-made ATACMS missiles early Tuesday at a military facility in Russia's Bryansk region that borders Ukraine, adding that air defenses shot down five of them and damaged one more. Ukraine's military claimed the strike hit a Russian ammunition depot.

While the doctrine envisions a possible nuclear response by Russia to such a conventional strike, it is formulated broadly to avoid a firm commitment to use nuclear weapons and keep Putin's options open.