Should Ukraine have nuclear weapons? This is a question that was raised, a little insincerely, by President Zelensky recently as he discussed Nato membership and its alternatives. If Ukraine was not in Nato, Zelensky mused, the only alternative would be to look for protection of another kind: nuclear arms. A recent story in the Times said that Ukraine could make a ‘rudimentary’ nuclear bomb ‘within months’ if Donald Trump withdrew Ukraine’s military assistance.

Russia has not used its nuclear weapons, but they have been the major reason no western power has directly intervened on Ukraine’s side. Ukraine had its own nuclear arsenal after the fall of the Soviet Union left it with a significant stockpile. If there is one thing every Ukrainian agrees on, it is that Ukraine should not have given up its bombs, which it did at the time of the 1994 Budapest memorandum. Ukraine joined non-proliferation treaties in return for a guarantee of Ukraine’s independence signed by Russia, Britain, France and the United States.

Ukraine gave up its capacity to stop a Russian invasion, and got invaded anyway – twice. Those guarantees were worthless pieces of paper. Ukraine could not have afforded to keep its nuclear weapons, but as missiles rain down on the country night by night, those in shelters dream of a better world.

But would nuclear weapons help Ukraine? Not really. Nuclear powers are attacked and lose wars all the time. The USSR and then America and Britain fought lost wars in Afghanistan without considering a nuclear option. The United States gave up a kind of victory in Korea by foregoing the bomb. Russia has already invaded Ukraine. A nuclear deterrent might work if that war were over and Russia threatened another attack, but it is not over.

Could Ukraine develop nuclear weapons? The basic science is 80 years old and nuclear programmes have been built in the past by poor and isolated countries. Israel, South Africa, India, Pakistan, Iran, North Korea all built bombs or got extremely close in difficult circumstances. China’s first bomb came when the population was unfathomably poor. It is technically possible. But nuclear development is expensive.

In the minds of the American president and his national security officials, the war in Ukraine is mostly a war about stopping the use of a nuclear weapon. According to a new book by Bob Woodward, there were moments in the dark days of 2022 in which the Biden White House thought the chance of Russia using a tactical nuclear weapon was about 50:50. It took months, and the election of Donald Trump, for Biden’s government to approve Ukraine’s use of long-range missiles inside of Russia.

In fact, lots of America’s dealings with despotic states revolve around trying to avoid them using nuclear weapons. North Korea’s army-first policy guarantees that as long as the Kim regime remains, there will never be a shortage in nuclear funding. The Islamic Republic’s Revolutionary Guards control not only Iranian war policy, but also much of its economy. So long as they remain, so too will the nuclear programme.

A new worry is the threshold or ‘virtual’ nuclear powers. States that know they would be isolated and sanctioned into oblivion if they openly carried out a nuclear test or violated non-proliferation, but who have the money and will to get as close as possible to a bomb to extort everyone else. They might finish one and use it. Who could say?

This is a real problem. Many states could do this, if they had the money and were prepared to tolerate the assassinations, espionage, dirty tricks of all kinds, that would come their way once it leaked out that this is what they were doing.

Japan and South Korea are apparently considering nuclearisation as China pursues the largest nuclear build-up of this century. A finished Iranian nuclear weapon would be followed, we are told, by a Saudi one in record time.

Zelensky appeared to be joking, using dark humour to muse on the ways his country has been betrayed and let down in the past. What he wants is not to be betrayed again. He would rather have a defence pact than a bomb, even though last time his country traded one for the other, and ended up with neither.