Russia’s invasion of Ukraine and nuclear sabre-rattling against the West have revived a debate about nuclear weapons. Last year, when a United Nations treaty to ban such weapons outright entered into force, none of the world’s 9 nuclear-weapons states were among the 86 signatories. How can these states justify possessing weapons that put all of humanity at risk?

That is a pertinent question, but it must be considered alongside another one: If the United States were to sign the treaty and destroy its own arsenal, would it still be able to deter further Russian aggression in Europe? If the answer is no, one also must consider whether nuclear war is inevitable.

It’s not a new question. In 1960, the British scientist and novelist C P Snow concluded that nuclear war within a decade was “a mathematical certainty”. That may have been an exaggeration, but many believed Snow’s prediction would be justified if a war occurred within a century. In the 1980s, Nuclear Freeze campaigners like Helen Caldicott echoed Snow in warning that the build-up of nuclear weapons “will make nuclear war a mathematical certainty”.