As he was leaving the Oval Office, Barack Obama warned Donald Trump that nuclear-armed North Korea would be his most immediate foreign policy challenge. That looked prescient on Monday, when Pyongyang fired five ballistic missiles into the Sea of Japan.

North Korea is a country with bad cards, which it plays well. For decades, it has terrorised its neighbours and their allies into negotiations and concessions, while continuing to act with bad faith and impunity. Mr Trump’s most visible response so far has been a tweet casting aspersions on the dictatorship’s military capabilities. One hopeful sign, however, is that the US president seems to understand that China is the key to reining in this recalcitrant Stalinist dynasty.

North Korea has been a Chinese client state for decades, but Beijing is struggling to restrain the regime. This week’s launches were timed to coincide with the annual meeting of China’s rubber-stamp parliament, sending a message to Beijing that the youthful dictator Kim Jong Un is unhappy with his main benefactor.