When the Khmer Rouge came to power in Cambodia in 1975, they inherited a war-ravaged and internationally isolated country. Pol Pot s government espoused the rhetoric of self-reliance, but Democratic Kampuchea was utterly dependent on Chinese foreign aid and technical assistance to survive. Yet in a markedly asymmetrical relationship between a modernizing, nuclear power and a virtually premodern state, China was largely unable to use its power to influence Cambodian politics or policy. In Brothers in Arms, Andrew Mertha traces this surprising lack of influence to variations between...