When Joe Biden meets South Korean and Japanese diplomats today in Hawaii for three-way talks, coping with the North Korean nuclear peril will be the main topic. The American vice-president will be able to commend the three navies for their first co-ordinated joint missile-tracking drill, “Pacific Dragon”, based on hypothetical North Korean launches, conducted off Hawaii in late June. Having finally agreed to adopt an American-funded THAAD (Terminal High-Altitude Area Defence) missile-defence system, South Korea now plans to have it up and running within 18 months. Such international co-operation is urgent: North Korea has lately been firing off its Musudan missiles with gusto. Their 3,000-3,500km range covers South Korea, Japan—and even, perhaps, American military bases on Guam. Most have fizzled after lift-off or crashed into the sea. But the latest, in June, soared higher than any previous missile from the rogue state. Heightened tensions indeed.