Effects of religious norms on interstate armed conflict are understudied compared to such effects on intrastate conflict. Yet religion exerts no less influence on states’ preferences and outcome of interstate interaction than other factors. Religion fosters emotion, in turn generating cognitive and motivational biases in states’ leaders. Religion acts as a political ideology that inculcates worldviews and programs political agendas. Religion accomplishes these things through scripture, clergy, and historical narrative. Through these media, religion instills standards of behavior, including for resort to (political) violence. Thus, religions influence states’ propensities to initiate interstate armed conflicts, even when belligerents’ goals are not necessarily sacralized. However, different norms are ingrained in different religions, and median war ethics of different religions range from permissive to restrictive. Therefore, over time and space, different religions are expected to have different effects on initiation of interstate armed conflicts. Regressing that outcome against the newly introduced Government Religious Preference (GRP) scores for Christianity, Islam, and Buddhism reveals that such is the case; different religions are differently associated with war and peace.