Vladimir Putin could face a revolt within his own country if he were to launch an attack on the United States or the United Kingdom. This week saw a fresh escalation in tensions, with Washington and London authorizing Ukraine to use their long-range missiles on Russian territory.

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.

President Vladimir Putin said on Thursday that the Ukraine war was escalating towards a global conflict after the United States and Britain allowed Ukraine to hit Russia with their weapons, and warned the West that Moscow could strike back.

A decree signed by the Russian leader, though long planned, came days after President Biden authorized the use of U.S.-supplied missiles by Ukraine for strikes inside Russia.

President Vladimir Putin's spy chief warned the West on Wednesday that it risked disastrous consequences if the United States and its European allies stoke a direct military confrontation with Russia over Ukraine.

This week's saber rattling has come during a period in which the war has passed 1,000 days and at a pivotal moment in the conflict between Moscow and Kyiv.