The disciplined, top-down Chinese Communist Party, some 90 million strong, extends throughout the Chinese government, society, and economy like a nervous system: its health determines how well the central authorities can control what goes on in every part of the country. Scholars tend to think of the CCP as omnipresent, but Koss uses extensive archival and statistical research to show that its power varies from place to place. When the (now abandoned) one-child policy was in effect, for example, the ban on sex-selective abortions was implemented more fully where the local party apparatus was strong than where it was weak. Koss also shows that strong local party organizations are correlated with lower levels of tax evasion. But powerful local cells may also resist central policy more effectively than weak ones, as happened during the Great Famine of 1958–61 and the Cultural Revolution in the late 1960s. Surprisingly, variations in local party strength can be traced all the way back to the Sino-Japanese War of 1937–45, when peasant resistance to the Japanese spurred strong party growth in the areas immediately threatened by Japanese troops, whereas those areas outside the war zone did not have the same catalyst. Koss adds an important dimension to scholars’ understanding of how the Chinese system works—and of its vulnerabilities.