Smart weapons represent a key element of military power for countries around the world, and nothing symbolizes them more than smart bombs—the guided aerial bombs that the United States debuted in the Vietnam War. Yet, international relations scholars know little about these weapons and what explains their proliferation. In this paper, we theorize about the key drivers of smart bomb proliferation, including an interaction between the security environment, regime type, and the interest of states in precision to help them follow the law of war. We then introduce a new dataset on smart bombs from 1960-2017. The results show that internal and external security threats make countries more likely to acquire smart bombs. These effects interact with regime type and whether countries are more likely to ratify treaties related to the law of war. GDP per capita and economic capacity also appears fundamental to explaining smart bomb adoption.