Precision weapons such as drones have become important elements of the military strategies of the United States and other countries. How does the use of precision weapons influence public support for the use of force? The public is averse to casualties, mission failure, and collateral damage. I argue that precision weapons increase the salience and importance of avoiding civilian harm. Individuals adopt their expectations about the outcomes of using these weapons and have lower tolerance for attacks that result in civilian deaths. This proposition is consistent with the results of two survey experiments. In the first, the possibility of civilian casualties leads to larger declines in support for the use of force than do military casualties or mission failure. In the second, respondents primed with information about an attack with precision weapons exhibited less tolerance for civilian harm than those primed with other weapons systems, despite the fact that the outcomes described to all respondents were identical.