Donald Trump has had quite a week. At the G7 summit in Canada the US president repudiated the rules-based international order, preferring to throw a tantrum on trade. By Tuesday, he was discarding longstanding security guarantees to America’s east Asian allies at his headline-grabbing talks in Singapore with North Korean leader Kim Jong Un. The security of Europe and east Asia has been underwritten for 70 years by a US alliance system. Mr Trump is intent on dismantling it.

It takes a special talent even for this president to recast Canada as an adversary before embracing as a new-found friend a brutal dictator with a recently acquired nuclear arsenal. We should know not to measure Mr Trump against the usual norms. The chilling significance of these actions resides in the clarity they bring to his intentions.

China and Russia are throwing their hats in the air to celebrate the president’s retreat from international leadership. Absent from the Singapore summit, Xi Jinping, the Chinese president, was nonetheless a big winner. In Mr Trump’s world of everyone for themselves, China will replace the US as the pre-eminent power in east Asia. Japan, Taiwan and, in time, South Korea itself, may choose to take a tip from Mr Kim. If you want to be safe, build a bomb.