Using newly available archival sources, Two Suns in the Heavens examines the dramatic deterioration of relations between the USSR and China in the 1960s, whereby once powerful allies became estranged, competitive, and increasingly hostile neighbors. Sergey Radchenko's authoritative account of these years shows how the intrinsic inequality of the Sino-Soviet alliance--seen as entirely natural by the Russians but bitterly resented by the Chinese--resulted in its ultimate collapse. Through a careful and comprehensive investigation of policymaking in both Moscow and Beijing, Radchenko creates a new framework for understanding the role of power struggle, ideology, personalities, and culture in Sino-Soviet relations.