At first glance, Beijing’s designation of an air defence zone in the East China Sea marks a calibrated escalation of its longstanding dispute with Japan about sovereignty of the Senkaku or, in Chinese, Diaoyu islands. A more worrying, and plausible, interpretation is that Beijing has decided to square up to the US in the western Pacific. East Asia is looking an ever more dangerous place.

When Xi Jinping met Barack Obama in California earlier this year, the Chinese president told his US counterpart the Pacific Ocean was large enough to accommodate two great powers. The inference was that the US and China should divide the spoils. Also implicit in the remark, though, was that China would not accept a status quo that saw the US remain the Pacific’s pre-eminent power. At the summit, Mr Obama sidestepped the issue. Now it seems Mr Xi has decided it is time for China to start grabbing its share.

The Senkaku have been administered by Japan since the late 19th century, apart from a spell of US control after the second world war. China restaked a claim during the early 1970s, but for decades did little to press its case. Since the 2008 Olympics, Beijing has adopted a more assertive approach, making regular incursions into the disputed territory’s sea and air space. This has prompted a US warning that the area is covered by the US-Japan mutual security pact.