Putin's chilling new nuclear doctrine; a closer look at new threats and scenarios

President Vladimir Putin has approved changes to Russia's nuclear weapons policy, and Moscow has urged the West to study them closely.

What's new, why is it happening now, and what does it mean for the war in Ukraine?

What just happened?

Putin signed a decree on Tuesday updating Russia's nuclear doctrine, last published in 2020. The seven-page document, like the one it replaces, says Moscow sees nuclear weapons as a means of deterring its enemies and sets out the scenarios under which it would consider using them.

Was this unexpected? Why did Russia announce it now?

The document's content was no surprise because Putin had spoken publicly about the key points on Sept. 25. Tuesday's decree came on the same day that Ukraine fired U.S.-supplied ATACMS missiles into Russia for the first time in the war, a step Moscow sees as a major escalation. But some security analysts played down the timing, saying it was understandable that the state bureaucracy had taken weeks to draft and publish the document following Putin's instructions.

How does the new doctrine apply to the Ukraine war?

It states that any aggression against Russia by a non-nuclear state that is carried out with the participation or support of a nuclear state will be considered a joint attack. This is important because Putin has said that Western countries would be fighting Russia directly if they allowed Ukraine to fire deep inside Russia with missiles they had supplied to Kyiv.

It lists additional scenarios under which Moscow would consider a nuclear response, including if it had reliable information about the launch of a massive cross-border air attack on Russia using planes, missiles and drones. Ukraine has staged frequent air attacks, mostly with drones but now also with US missiles, to degrade Russia's ability to strike Ukrainian troops, cities and energy infrastructure.

What are the other key changes?

Much of the language is unchanged from 2020, but there are a number of alterations and additions that in effect lower the threshold for Russian nuclear use.

Russia is officially placing close ally Belarus under its nuclear umbrella, after Putin announced last year he was stationing Russian tactical nuclear missiles there.

Russia now says it may use nuclear weapons in the event of a conventional attack against itself or Belarus that "creates a critical threat to their sovereignty or territorial integrity".

Previously, Russia had said it might meet a conventional attack with nuclear weapons "when the very existence of the state is placed under threat".

Russia says its nuclear deterrent is aimed not only at other nuclear states but also at other countries that allow their land, water or airspace to be used to prepare or conduct aggression against it.

Russia has removed language in the previous version that listed "observance of international obligations in the area of arms control" as one of its principles of nuclear deterrence.

What other threats could prompt Russia to go nuclear?

The document lists several new risks and scenarios that were not mentioned in the 2020 doctrine and which it says could prompt Russia to consider a nuclear response:

Creation of new military coalitions, or expansion of existing ones, that move enemy military infrastructure closer to Russia's borders;

Actions aimed at cutting off or blockading part of Russia; Actions aimed at causing an ecological catastrophe; Planning or carrying out large-scale military exercises near Russia's borders;

Attacks using nuclear weapons or other weapons of mass destruction on Russian forces deployed outside Russia's borders.

So what is Putin trying to tell the west?

The new doctrine contains no major surprises, given Putin's previous public statements. But it fits into a long pattern of warnings that the U.S. and its allies risk entering a direct conflict with Moscow that could turn into World War Three if they keep stepping up support for Ukraine.

It comes at a moment of acute tension, with Ukraine, South Korea and the U.S. saying North Korean troops are entering the war on Russia's side - something Moscow has not denied - and with both Russia and Ukraine seeking to strengthen their positions ahead of Donald Trump's return to the White House and the possibility of negotiations to end the war.

Western governments say they will not be intimidated by Russia, with the U.S. rejecting "more of the same irresponsible rhetoric from Russia" and saying it sees no reason to adjust its own nuclear posture. France's foreign minister described the Russian move as just "rhetoric" and Ukrainian President Volodymyr Zelenskiy expressed concern about what he saw as Putin's lack of interest in peace.