Within a single conflict, the scale of government violence against civilians can vary greatly—from mass atrocities in one village to eerie restraint in the next. This article argues that the scale of anticivilian violence depends on a combatant’s relative dependence on local and external sources of support. External resources make combatants less dependent on the local population, yet create perverse incentives for how the population is to be treated. Efforts by the opposition to interdict the government’s external resources can reverse this effect, making the government more dependent on the local population. The article tests this relationship with disaggregated archival data on German-occupied Belarus during World War II. It finds that Soviet partisan attacks against German personnel provoked reprisals against civilians but that attacks against railroads had the opposite effect. Where partisans focused on disrupting German supply lines rather than killing Germans, occupying forces conducted fewer reprisals, burned fewer houses, and killed fewer people.