The intrusion of six Chinese ships into the Japanese-controlled waters surrounding the disputed Senkaku islands is just the latest escalation in the stand-off over an uninhabited archipelago in the East China Sea.
China's move follows Japan's recent purchase of three of the islands from their private owners, despite strong objections from Beijing, which claims sovereignty. Now China's ambassador in Tokyo has been summoned to explain himself, and protests outside the Japanese embassy in Beijing are growing.
Against a backdrop of generations of animosity (and several nasty wars), such developments are far from encouraging. More concerning still, the Senkaku are not China's only maritime flashpoint in the region. Disputes with Vietnam and the Philippines, and to a lesser extent Malaysia and Brunei, over rocky outcrops in the South China Sea have also flared back into life this year.
The US has repeatedly stressed its neutrality. But China remains suspicious of Washington's intentions, and the "pivot" of US military focus on to Asia/Pacific only emphasises the sensitivities of the region. All of which just adds to the tension. But it would be easy to jump to the wrong conclusion about China's new-found restlessness, at least in the short term.
It may be true that Beijing, buoyed by its rising economic power, is eager both to confirm its new-found status and to right the wrongs of China's "century of humiliation". And a hunger for the natural resources to be found in the seabed also no doubt has a role to play. But there are also powerful domestic forces at work.
In the aftermath of the Bo Xilai scandal (in which a favoured political son was ousted and his wife convicted of murder), with the once-in-a-decade leadership handover looming, and all-important economic growth markedly slowing, Beijing's immediate priority is to reaffirm the legitimacy of Communist rule. What better way to do so than by appealing to popular nationalism?
There is reason to hope, then, that the latest quarrels might lose some of their potency in the months ahead. But with little sign of a resolution to the competing claims behind them, there will be many more to come.