The world is not yet at war. But the relative peace that we enjoyed since the end of the last Cold War has gone. State-on-state aggression is back. My fear, though, is that we are in a Cold War far more complex and dangerous than the last. Then we had back channels, treaties and wise statecraft to prevent it turning hot. It contained a nuclear arms race to ensure no nuclear weapon, large or small, would ever be deployed. Those days are over. The back channels have gone, the treaties have lapsed, and the determination of dictators like Putin not to lose (believing the West will not respond) means a nuclear weapon will, in my view, be fired within the next decade. It may not come from an unexpected source – a country that has nearly acquired one, or a terrorist faction within a state – but the danger is very real.