What if Vladimir Putin used nuclear weapons in Ukraine?

President Vladimir Putin’s thinly veiled threat to use nuclear weapons in Ukraine if Russian “territorial integrity” is threatened has sparked deep discussion in the West as to how it would respond.

In a televised address on Wednesday, the Russian leader said he was not bluffing about using nuclear weapons if Russian territories were threatened, as he announced a partial military mobilisation that would see some 300,000 reserve forces sent to fight in Ukraine.

“Those who are trying to blackmail us with nuclear weapons should know that the wind can also turn in their direction,” Putin said, adding: “This is not a bluff.”

Analysts are not convinced that Putin is willing to be the first to unleash nuclear weapons since the United States dropped two atomic bombs on Japan in 1945.

Several experts and officials spoke with AFP about the possible scenarios that could arise should Russia carry out a nuclear attack.

What would a Russian nuclear attack look like?

Analysts say Moscow would likely deploy one or more “tactical” or battlefield nuclear bombs.

Tactical nukes are small weapons, ranging from 0.3 kilotons to 100 kilotons of explosive power, compared with the 1.2 megatons of the largest US strategic warhead or the 58 megaton bomb Russia tested in 1961.

Tactical bombs are designed to have a limited impact on the battlefield, compared with strategic nuclear weapons which are designed to fight and win all-out wars.

But “small” and “limited” are relative: The atomic bomb the US dropped on Hiroshima in 1945 to devastating effect was just 15 kilotons.

What might Moscow target?

Analysts say Russia’s goal in using a tactical nuclear bomb in Ukraine would be to frighten it into surrender or submission to negotiations, and divide the country’s Western backers.

Mark Cancian, a military expert with the Center for Strategic and International Studies (CSIS) in Washington, said Russia would not likely use nuclear weapons on the front lines.

Capturing 20 miles (32km) of territory could require the use of multiple nuclear bombs – small gains for the huge risks of introducing nuclear weapons and nuclear fallout.

“Just using one will not be enough,” Cancian said.

Moscow could instead send a strong message and avoid significant casualties by detonating a nuclear bomb over water, or exploding one high over Ukraine to generate an electromagnetic pulse that would knock out electronic equipment.

Or, Putin could opt to attack a Ukrainian military base, or hit an urban centre and generate mass casualties and possibly kill the country’s political leadership.

Such scenarios “would likely be designed to split the NATO (North Atlantic Treaty Organization) alliance and global consensus against Putin,” Jon Wolfsthal, a former White House nuclear policy expert, wrote on Friday on Substack.

“It is unclear if it would succeed, and could just as easily be seen as desperation as resolve,” he said.

How should the West respond?

The West has remained ambiguous on how it would respond to a tactical nuclear strike, and the choices are complicated.

The US and NATO do not want to appear weak in front of an implicit nuclear threat. But they also would want to avoid the possibility that the war in Ukraine – not a NATO member – could escalate into a much broader, devastating global nuclear war.

Experts say the West would have no option but to respond to a Russian nuclear attack, and that a response should come from NATO as a group, rather than the US alone.

The US has positioned about 100 of its own tactical nuclear weapons in NATO countries and could respond in kind against Russian forces.

The threat of response would demonstrate resolve and remind Moscow of the danger of its actions, according to Matthew Kroenig of the Atlantic Council.

However, he said, “it might also provoke a Russian nuclear reprisal, raising the risk of a larger nuclear exchange and further humanitarian disaster”.

Another risk is that some NATO members might reject a nuclear response, serving Putin’s aims of weakening the alliance.

Should Ukraine be given more powerful weapons?

Answering a nuclear attack in a more conventional military or diplomatic way, and supplying Ukraine with more lethal arms to attack Russia, could be more effective, experts say.

“Russian nuclear use might provide an opening to convince countries that have so far been reluctant – such as India and possibly even China – to participate in escalating sanctions,” Kroenig said.

In addition, the US could offer Ukraine NATO aircraft, Patriot and THAAD anti-missile batteries, and ATACMS long-range missiles that could be used by Ukraine forces to strike deep inside Russia.

“Whatever restrictions we have on Ukraine forces – and I think we have some restrictions – I think we take all of those off,” Cancian said.