This study evaluates the impact of an intimate partner violence prevention program in Rwanda, using a randomized controlled trial. The 22-week couples training program aimed to improve communication, shift gender attitudes, and promote gender equality. Randomizing at both the village and couple levels, the study finds that the program caused large, unexpected increases in intimate partner violence. Treated women reported 5 and 10 percentage points more physical and sexual violence than control women, respectively, and control women living in treated villages reported even larger increases of 11 and 17 percentage points. Evidence suggests that these increases stem from male backlash against perceived identity threats, as women's more progressive attitudes and aspirations contrast with men's pressure to maintain traditional norms, generating friction within households. Innovative measurement techniques and extensive robustness checks show that changes in reporting behavior cannot explain the results.