The violent anti-Japanese protests in Beijing and two southern cities at the weekend were the biggest demonstrations in China for six years, and clearly took place with tacit government encouragement. The attacks on two Japanese students, the bottles, stones and abuse hurled at the Japanese Embassy and residence by an estimated 20,000 protesters and the burning of Japanese flags have infuriated Tokyo and embarrassed the Chinese Government, which generally has a fear of demonstrations. But there was no disguising its use of the mob to put pressure on Japan at a time of rising tensions: an official statement blamed worsening relations on Japan’s failure to atone for its wartime past.

The pretext is the decision by a few Japanese middle schools to use some history books next year that gloss over Japanese wartime atrocities — describing the Nanking massacre, for example, as an “incident”. But Chinese resentment goes deeper, and focuses on what it sees as the repeated failure of Japanese leaders and society to make a full apology for their wartime record or to accept the moral responsibility. As evidence, China cites the visits by Junichiro Koizumi, Japan ’s Prime Minister, to the Yasukuni shrine honouring all Japanese war dead, including war criminals.

Resentment of Japan’s insouciance over the past is widespread, and not confined solely to China: South Korea has also objected to the textbooks and Japan’s paltry efforts at atonement for Korean “comfort women”, forced into wartime military brothels. But China has exploited and exacerbated historic bitterness for political purposes: first, to divert attention from domestic tensions over economic disparities, unemployment, corruption and political restrictions; and secondly, to limit Japan’s influence in Asia at a time of growing political and economic competition with China.

One target this time is Japan’s expanded defence treaty with America, which Beijing sees as a sign that Tokyo is becoming more assertive. It is especially angered by Japanese endorsement of US moves to inhibit Chinese military pressure on Taiwan, which was colonised by Japan in 1895. The Communist Party is now playing a nationalist card to win backing at home. But creating an atmosphere viscerally hostile to Japan, which some Chinese companies no doubt hope will blunt Japanese competition, could have dangerous consequences.

Japanese opinion is no longer so subservient. Aid to China has ended, and Mr Koizumi, fearful of challenge to his Liberal Democratic Party on the Right, is in no hurry to visit Beijing. Trade is flourishing, as is Japanese investment in China, regardless of Beijing’s bluster. But the economic relationship could well be threatened. Mr Koizumi must prove that he is a genuine reformer by finding a different ceremony to honour the nation’s war dead and to ensure that the annual ritual of textbook tension is brought to an end. Meanwhile, China’s leaders must understand that they will be the ultimate losers if they encourage a marauding mob mentality.