Joe Biden began his week in Japan, where Tokyo’s politicians are furious at China; he then flew into Beijing which is seething about Tokyo’s behaviour; and tomorrow he is due in South Korea, which is irate at both China and Japan. Welcome, Mr Vice-President, to East Asia’s new normal.

Two weeks ago, few people had ever heard of “air defence identification zones”, the Cold War-era set of regulations that China has decided to put in place across a large stretch of the East China Sea. But the obscure rules have become the latest flashpoint in the region’s unresolved disputes. By the end of the week, Air Force Two will probably have passed twice through the world’s most controversial airspace.

The air rules are part of a pattern: steady Chinese pressure to push its claims over disputed territories, particularly the islands Japan calls the Senkaku and China the Diaoyu. Since around 2008 China has been sending ships to patrol the seas around them. The air zone extends its claim to the skies above.