Does warfare affect the environment? This question has received some theoretical and empirical attention, but none of the extant studies has employed large-N statistical models. This article theorizes the possible effects of warfare on the environment and estimates large-N statistical models of these effects on CO2 emissions per capita, NOX emissions per capita, the rate of change in forested area, and a composite indicator of environmental stress reduction. The results indicate that warfare significantly affects the environment, but the signs and sizes of these effects depend on the environmental attribute (whether the fighting is at home or abroad) and development (whether the fighting country is developed or less developed). Warfare reduces CO2 emissions, but the effect is weaker in less developed countries (LDCs) than in developed countries (DCs). Warfare increases deforestation when fought at home and promotes forest growth when fought abroad, particularly in the LDCs. Warfare at home reduces NOX emissions for the LDCs and increases them for the DCs; warfare abroad increases NOX emissions for both the DCs and LDCs. Finally, warfare increases aggregated environmental stress, particularly for the LDCs when fought at home and for the DCs when fought abroad. The sizes of these effects are on par with or larger than the mandated or recommended policy goals stated by the US government for changes in CO 2 and NOX emissions, and by the World Bank (and by implication the DCs driving its policy) for the rate of deforestation, during the coming decade.