The territorial dispute between Japan and China over uninhabited islands in the East China Sea just got more dangerous. At the weekend, Beijing continued its strategy of slowly ratcheting up the pressure on Tokyo when it declared an “air defence identification zone” covering airspace over the disputed islands. Aeroplanes entering the zone will need to identify themselves or face what Beijing said would be “defensive emergency measures”. Given that Japanese aircraft regularly patrol the area in what Tokyo considers its own airspace, Beijing’s move appears to increase the chance of a clash, accidental or otherwise.

The dispute over the Japanese-controlled islands, called Senkaku by Tokyo and Diaoyu by Beijing, dates back to the late-19th century when China says Japan stole them in war. Tokyo says that the islands were legally incorporated into its territory in 1895 after it discovered them to be no-man’s land. China says they have been part of its territory since ancient times and should have been returned after 1945. Beijing appears to want to force Tokyo to concede that the islands are disputed, something that it does not accept.

Whatever its claims to the islands, Beijing is acting foolishly. Like it or not, they have been administered by Japan for well over 100 years, save when the US controlled them as part of Okinawa between 1945 and 1972. China is seeking to change the status quo by intimidation. The islands are situated in important submarine lanes and controlling them would help Beijing fulfil its naval ambitions to break beyond its coastal waters. It would also settle a historical score. The escalation is doubly dangerous since the islands are covered by the US-Japan security treaty, implying that Washington is committed to helping defend them.