Putin Lowers Nuclear Weapons Threshold After U.S. Allows Ukraine to Use Missiles Against Russia

President Vladimir V. Putin on Tuesday lowered Russia’s threshold for the use of nuclear weapons, a long-planned move whose timing appeared designed to show the Kremlin could respond aggressively to Ukrainian strikes on Russian territory with American long-range missiles.

The decree signed by Mr. Putin implemented a revised version of Russia’s nuclear doctrine that Mr. Putin described in televised remarks in September. But the timing was clearly meant to send a message, coming just two days after the news that President Biden had authorized the use of U.S.-supplied long-range missiles by Ukraine for strikes inside Russia.

Asked whether Russia could respond with nuclear weapons to such strikes, Dmitri S. Peskov, Mr. Putin’s spokesman, repeated the new doctrine’s language that Russia “reserves the right” to use such weapons to respond to a conventional-weapons attack that creates a “critical threat” to its “sovereignty and territorial integrity.”

The new doctrine asserts that Russia could use nuclear arms in the event of an attack by a nation backed by a nuclear power. The doctrine’s publication on Tuesday appeared to be the latest suggestion from the Kremlin that Russia could use nuclear weapons to respond to attacks by Ukraine carried out with American support, and that the response could be directed against American facilities as well as Ukraine itself.

“Aggression against the Russian Federation and (or) its allies by any nonnuclear state with the participation or support of a nuclear state is considered as their joint attack,” the document says.

Mr. Peskov, speaking at his daily conference call with reporters, pointed to this section of the revised doctrine, saying, “this is also a very important paragraph.”