The conventional wisdom suggests that states with nuclear energy programs are more likely to seek or acquire nuclear weapons. Yet there is a dearth of systematic empirical work that directly assesses this proposition. A systematic analysis of the historical evidence suggests that the link between nuclear energy programs and proliferation is overstated. Although such programs increase the technical capacity of a state to build nuclear weapons, they have important countervailing political effects that limit the odds of proliferation. Specifically, nuclear energy programs increase the likelihood that parallel nuclear weapons programs will be detected and face counterproliferation pressures; they also increase the costliness of nonproliferation sanctions. Contrary to the conventional wisdom, states with nuclear energy programs historically have not been significantly more likely to seek or acquire nuclear weapons. A combination of qualitative and quantitative evidence supports the plausibility of the countervailing political effects of nuclear energy programs.

How has the United States behaved historically toward friendly states with nuclear weapons ambitions? Recent scholarship has demonstrated the great lengths to which the United States went to prevent Taiwan, South Korea, and West Germany from acquiring nuclear weapons. Yet seemingly on the other side of the ledger are cases such as Israel, South Africa, and Pakistan, where the United States failed to prevent proliferation, and where many have argued that the United States made exceptions to its nonproliferation objectives given conflicting geopolitical goals. A reexamination of the history of U.S. nonproliferation policy toward Israel, South Africa, and Pakistan, based on declassified documents and interviews, finds that these cases are not as exceptional as is commonly understood. In each case, the United States sought to prevent these states from acquiring nuclear weapons, despite geopolitical constraints. Moreover, once U.S. policymakers realized that prior efforts had failed, they continued to pursue nonproliferation objectives, brokering deals to prevent nuclear tests, public declaration of capabilities, weaponization, or transfer of nuclear materials to other states.