A third review of The China–Pakistan Axis: Asia’s New Geopolitics' by Andrew Small, by Myra Macdonald (who is always worth reading):http://warontherocks.com/2015/02/not.../?singlepage=1

A passage of note refers to Xinjiang, an issue that grown IMHO in recent years:
Until relatively recently, moreover, it was able to rely on Pakistan’s Inter-Services Intelligence (ISI) agency to gain access to the Afghan Taliban and other Islamist militants to ensure Chinese interests were left alone and Uighur militants from its Xinjiang region kept in check. But as Pakistan began to lose its grip on Islamist militants, China also lost some of its confidence in Pakistan. At home, China has faced increased attacks from Uighur militants; while in both Pakistan and Afghanistan, Chinese workers have been killed. Hence its worries about the Pakistan Army: it is one thing to support a national military against India and quite another to supply one being eaten away from within by a virulent strain of violent Islamism.

(China)...it also has common cause with Washington in its desire for regional stability. Indeed it was U.S. drone strikes rather than Pakistani troops that killed Uighur militant leaders wanted by China in the Federally Administered Tribal Areas (FATA) of Pakistan.