Andrew Small's analysis of recent developments in Sino-Pakistan relations in his book The China-Pakistan Axis: Asia's New Geopolitics is insightful and persuasive. Small's central thesis, as I understand it, is that around 2013 China significantly shifted its policy for managing its vital relationship with Pakistan. Motivated both by the metastasis of Islamic extremism across the region and by deepening understanding of the impact that a possible India-Pakistan nuclear war would have on that spreading extremist cancer, China set aside its earlier policy of noninterference in Pakistan's affairs. It began urging Pakistan's leaders to rein in extremist groups, not only those mucking around in China's Xinjiang region (which Beijing had long warned Islamabad against), but even within Pakistan and Afghanistan. Beijing recognized the diminishing utility of secret side deals worked out with extremist groups in years past. Such deals simply did not work as well with the generation of extremist leaders-a conclusion attested to by the more frequent attacks in Xinjiang and on Chinese interests in Pakistan. Beijing also signaled to Islamabad that its support for Pakistan in a future confrontation with India would be conditioned by Pakistan's role in provoking that confrontation. This shorter leash was an attempt to dissuade elements in the fragmenting Pakistani state from again condoning terrorist attacks on India that threatened to trigger Indian retaliation and thence an India-Pakistan war that could further destabilize the entire region.This approach expanded diplomatic common ground with the United States in countering the spread of Islamic extremism and the disintegration of the Pakistani state. Derivatively, Beijing attempted to mediate a search for political accommodation in Afghanistan and adopted a more relaxed view toward the U.S. military presence there. Lord, make them [the Americans] leave, but not yet, became the Chinese mantra, Small suggests.Scholars will need to test Small's thesis of a major shiftin China's Pakistan policy through further primary research. But at a minimum, the book's clear, thoughtful, and empirically substantiated argument has advanced our knowledge of an important issue. Small posits two primary factors driving the shiftin China's Pakistan policy: (1) greater fragmentation of the Pakistani state and use of Pakistani territory as a base for Islamist operations, and (2) a rethinking of the implications of a possible India-Pakistan nuclear war.Regarding the first factor, the growing frequency of violent protests in both Xinjiang and major Chinese cities outside Xinjiang, combined with extremist attacks on Chinese citizens in Pakistan (e.g., construction crews refurbishing the Karakorum Highway, academics conducting research, or women operating massage parlors) indicated to Beijing that China's traditional reliance on Pakistan's military and political elites to minimize such incidents was simply no longer effective. The generation of extreme Islamist leaders is more ideological and less pragmatic than the older generation, with whom a deal might stick. The collapse of states such as Syria, Iraq, and Libya, together with the looming U.S. withdrawal from Afghanistan and the prospect of renewed civil war there, caused China to give much greater emphasis to internal security concerns arising out of its deeply rooted Uighur problem. In short, these concerns increasingly influenced China's management of its all-weather relationship with Pakistan. The spread of terrorist movements in the post-Soviet countries of Central Asia also threatened to undermine the ambitious transport-building programs of the new Silk Road designed to draw those lands into China's economic sphere and foster stability through faster economic growth.Regarding the nuclear factor, Small persuasively argues that, starting with the Kargil confrontation of 1999, Beijing recalculated the region-wide destabilizing effects of a nuclear exchange between India and Pakistan. …