Theories and counterinsurgency doctrines emphasize the importance of avoiding civilian casualties. Yet, many operations produce large numbers of so-called collateral civilian deaths. I present two competing arguments for when collateral deaths occur. One the one hand, they could be the unintentional result of offensives when trying to maintain force protection; on the other hand, they could be the result of a deliberate choice of relying on indiscriminate violence when pressured on the battlefield. I use new data on violence in Afghanistan 2004–2009, disaggregated by province and month, to examine what type of battlefield dynamics are more likely to produce high levels of collateral civilian casualties. The results show that civilian casualties are particularly high after counterinsurgency forces suffer losses in combat.