«Safety is our top con-cern », said China?s Vice-President Xi Jin-ping in late July, pointing to the deployment of 100,000 troops around Beijing and the surface-to-air missile batteries that protect the main stadiums as proof of the regime?s determination to ensure that no terrorist attack would disrupt the Olympic Games. But it couldn?t stop two determined Uighur militants from killing sixteen Chinese police and injuring another sixteen in an attack on a border post.

If two men armed only with hand grenades and knives could do that much damage there, what is to stop others from doing it in Beijing ?

The best way to prevent terrorist attacks is to remove the grievances that often motivate them, and to penetrate the terrorist organisations with informers. China hasn?t done very well on either front. In Xinjiang as in Tibet, it has inundated the local population with a wave of Han Chinese immigrants who live far more prosperous lives, and created great resentment as a result.

Ironically, the reason for the influx of Han Chinese immigrants is an effort to quell separatist sentiments in the two provinces. Most Chinese believe that their country has ruled Tibet and what used to be called East Turkestan since time immemorial, but in practice they only came under Chinese control in the mid-18th century, around the same time that the British were seizing control of India.

So if Beijing doesn?t want its territories to go the way of British India, then it must find a way to bind Tibetans and Uighurs to China. The solution, Beijing reckoned, was lots of development and rising prosperity, which would reconcile both Tibetans and Uighurs to Chinese rule.

Maybe it would have, too, if the subject peoples had shared in the prosperity, but they didn?t. Educational levels and technical skills were gravely lacking in the indigenous populations, so the real effect was to draw in millions of Chinese immigrants who did have the skills.

In 1945, ninety percent of Xinjiang?s population were Uighurs, a Muslim, Turkic-speaking people who are closely related to the other Muslim populations of Central Asia. Now the Uighurs are down to eight million out of nineteen million : less than forty-five percent of the population and falling fast.

As in the case of Tibet, there has been very rapid urbanisation, but most of the native population lives in ghettoes that are little better than slums, with no hope of getting the good jobs that are monopolised by Chinese immigrants. The difference between the two regions is that in Xinjiang there have been sporadic terrorist attacks against Chinese people and interests since the early 1990s.

Tibet is isolated by geography, culture, religion and language. It has no strong affinities with anywhere else, which largely explains its relative political passivity be-tween the 1959 revolt and this year?s disturbances. By contrast, Uighurs have strong historical, cultural, religious and linguistic links with the other Central Asian groups ? all of which got their independence when the Soviet Union collapsed in 1991.

That example, of course, was very seductive, and so a wide variety of Uighur separatist groups have carried out terrorist attacks both in Xinjiang and in China proper over the past two decades. The rise of « Islamist » terrorism latterly has given them a more coherent ideology than nationalism, and also some useful contacts in the distant parts of the Muslim world. They have only killed a couple of hundred people in twenty years, but they remain a serious headache for the Chinese regime.

So could Uighur separatists, or even Tibetan ones, carry out a terrorist attack in Beijing during the Olympics ? Of course they could. Nothing too spectacular, of course. No hijacked airplanes crashing into stadiums. But two men with grenades could do a lot of damage, and even 100,000 troops would need some luck to stop them.