Update, 13 December: Japan has accused China of violating its airspace in a worrying escalation of the bitter dispute over a set of small rocky islands in the East China Sea, known as Senkaku in Japan and Diaoyu in China. Japan says it is the first time a Chinese government aircraft has intruded on Japanese airspace since the Japanese military started keeping records in 1958.
Japan scrambled fighter jets in response and summoned the Chinese ambassador in Tokyo to hear a formal protest over the action, which China maintains was a "completely normal" flight pattern. But coming on the 75th anniversary of the start of the Nanjing massacre, in which Japanese troops killed tens of thousands of Chinese civilians in China's old capital, Nanjing, in 1937 – and just days before Japanese go to the polls to elect a new government, the timing could not have been more sensitive.
The squabble of the islands' sovereignty is an old controversy that reignited spectacularly over the summer, with nationalist protests spreading to over 50 cities across China and Tokyo in mid-September.
But is this conflict really just about a group of isolated rocks?
What are the facts?
The small group of uninhabited islands and barren rocks were never a major controversy – until oil and gas discoveries in 1969 and fishing grounds made them important.
Japan has controlled them for over 100 years, apart from a period of US administration, but China has not stopped claiming sovereignty.
Tensions rose over the summer after Japan moved to buy the islands from a private Japanese owner – putting them under direct government control.
Since then, Chinese ships have repeatedly entered the waters around the island in protest, ensuring small-scale but high-stakes naval standoffs with Japanese vessels.
Tensions are high, with thousands of Chinese protesters targeting the Japanese embassy and businesses, and 800 Japanese protesting against China in Tokyo.
What's behind the conflict?
Japanese prime minister Yoshihiko Noda's purchase of the islands was in part an attempt to head off growing pressure from far-right nationalist Tokyo mayor Ishihara Shintaro, who had launched his own public fund to buy the islands – a nightmare scenario. But Noda is not merely a victim. There are also political advantages for him in playing to the conflict, after an unpopular sales tax hike last month saw his approval rating plummet.
The Chinese Communist party is also on edge, ahead of the once-a-decade transfer of leadership later this year, and as the fallout of the corruption and murder scandal which brought down the once-powerful Chonqing mayor Bo Xilai continues. Slowing economic growth, increasing social divides and growing middle class dissatisfaction with China's environment all have the party concerned – and they do not want to be seen as weak in the face of anti-Japanese sentiment.
The islands' oil resources may account for the governments' original interests in these rocks, but it's nationalism that is driving the current conflict. Once a useful political tool encouraged by the Chinese and Japanese governments, nationalist sentiment has now forced them into a dangerous game they don't want to play.
Why all the hate?
These tensions were not hard to stoke. Before their defeat in the second world war, imperial Japan built an empire that included Taiwan, Korea and large parts of China. Wartime atrocities committed by Japanese troops, including the Nanking Massacre, remain sensitive – and Japan has failed to unambiguously apologise for their conduct.
As China has eclipsed Japan as Asia's pre-eminent economic power, the relationship has changed, and China is increasingly determined to expand its influence in the Asia-Pacific region.
Anti-US sentiment in China is also a key part of the mix. Many Chinese resent the US's strong alliance with Japan and the outsized role it allows Japan to play. A shift in US military priorities towards the Pacific also raises Chinese fears that the US will try to "contain" what they see as their rightful rise – with the US explicitly warning China that they consider the islands part of their security pact with Japan.
The incentives for both countries to peacefully resolve the conflict are strong: their economies are tightly interwoven and a military conflict could be devastating for both countries. But by playing to the nationalist mood that they have both wilfully cultivated in the past, the leadership of China and Japan are lighting a fuse they may not be able to extinguish.
This is a plain example of where diplomacy and cool-headed negotiations are desperately needed – and a clear articulation of why national interest for both countries means compromise, not conflict.
Learn more: Watch this excellent quick explainer from Al Jazeera, shot at the height of the September protests, which surveys the domestic political pressures driving China's actions:
Sources: BBC, New York Times, Wikipedia, Wall Street Journal, Reuters, Forbes, Asahi Shimbun, Straits Times