A top secret Russian nuclear base was placed on combat alert in the day Vladimir Putin ordered the full-scale invasion of Ukraine, a deserter has said.

The former Russian nuclear forces officer said before February 2022, the base where he worked only carried out exercises, but on the day the war began, “the weapons were fully in place”.

In a chilling insight, Anton, not his real name, told the BBC: “We were ready to launch the forces into the sea and air and, in theory, carry out a nuclear strike.”

According to the BBC, Anton fled Russia with the help of a volunteer organisation for deserters after refusing to participate in Putin’s war.

Moscow announced Russia‘s nuclear deterrence forces had been placed on a special mode of combat service three days after Putin’s troops invaded Ukraine. But Anton told the broadcaster the combat alert was in place from day one of the wider war.

He dismissed claims from some experts that Russia‘s nukes date from the Soviet period, arguing there may be some “old-fashioned” weapons, but the country has “an enormous” nuclear arsenal, with “constant” combrat patrols on land, sea and in the air.

Earlier this month, Putin signed a revised nuclear doctrine declaring a conventional attack on Russia by any nation supported by a nuclear power will be considered a joint attack on his country.

Putin’s endorsement of the new nuclear deterrent policy came on the 1,000th day after he sent troops into Ukraine on February 24, 2022.

It followed US President Joe Biden’s decision to let Ukraine strike targets inside Russia with US-supplied longer-range missiles.

Russia‘s doctrine says any massive aerial attack on the country could trigger a nuclear response. It also reflects Putin’s readiness to threaten use of the country’s nuclear arsenal to force the West to back down as Moscow pushes forward with its offensive in Ukraine.

The move appears to broaden the triggers for possible nuclear weapons use compared with the previous version of the document, which stated Russia could tap its nuclear arsenal if “reliable information” is received about the launch of ballistic missiles targeting Russian territory or that of its allies.

Hawks in Russia had been calling for toughening the doctrine for months, arguing the old version failed to deter the West from boosting aid to Ukraine and gave the impression Moscow would not resort to nuclear weapons.

Russia has 5,580 nuclear warheads, according to the Arms Control Association, citing figures from the Federation of American Scientists and others.

This compares to the United States (5,748), China (500), France (290), UK (225), India (172), Pakistan (170), Israel (90) and North Korea (50).

Russia has about 4,380 operational nuclear warheads, according to the Federation of American Scientists, with 1,700 reportedly ready for use.