The long read: With Putin’s threats in Ukraine, China’s accelerated weapons programme and the US’s desire for superiority, what will it take for leaders to step back from the brink?

Like Toto in The Wizard of Oz, at their 1985 summit in Geneva President Ronald Reagan and the Soviet leader Mikhail Gorbachev pulled back the curtain to reveal the truth behind the terrifying spectre of nuclear war, which their countries were spending hundreds of billions of dollars to prepare for. “A nuclear war cannot be won,” they jointly stated, and “must never be fought.” They omitted the inescapable corollary of those first six words: a nuclear arms race also cannot be won.