This dissertation examines the consequences of nuclear proliferation in South Asia by assessing the impact of maturing nuclear weapon capabilities on recent India-Pakistan relations. Its purpose is to deepen our understanding of proliferation dynamics on the Indian subcontinent, so that U.S. policy can better help to contain the region\u27s nuclear dangers. The study is conceptually framed by several important issues in the scholarly analysis of nuclear proliferation. First, it is embedded in a lively debate over the effects of proliferation. The orthodox position in this debate, which I call the logic of nonproliferation, considers the spread of nuclear weapons to be extremely dangerous: more weapons in more hands increase the likelihood of nuclear explosions. In contrast, the logic of nuclear deterrence suggests that proliferation is stabilizing: nuclear weapons have deterred war between their possessors and will continue to do so. Second, the study is theoretically situated in the analysis of opaque proliferation. Opaque proliferants publicly deny developing nuclear weapon capabilities, while secretly doing just that. This pattern has characterized every emerging nuclear power since the mid-1960s, but its implications are only now being fully realized. The project is driven by one central hypothesis: that existential nuclear deterrence has prevented war between New Delhi and Islamabad over the last decade. The hypothesis is derived from nuclear deterrence theory and an analysis of the logical nexus between opaque proliferation and existential deterrence. I then test the hypothesis in case studies of Indo-Pakistani behavior during two crises. I conclude that nuclear capabilities had little influence on the outcome of the 1986-87 Brasstacks crisis, which was resolved peacefully because there was no compelling political objective driving either side to a decision for war. On the other hand, I argue that the 1990 Kashmir crisis was resolved peacefully due to the influence of existential nuclear deterrence. My summary conclusion is that the Indo-Pakistani experience with nuclear weapons more closely matches the expectations of the logic of nuclear deterrence than the logic of nonproliferation