Although largely ignored by international relations scholars until the 21st century, religion has been and remains a pervasive social force both on and off the battlefield. It affects how combatants mobilize and prepare for war. It regulates how they fight, including unit organization and strategic decision making. In addition, religious identities, beliefs, practices, and symbols shape how and when combatants pursue peace. The study of religion and war seeks to discover and understand these varied influences, even when religion is not the pretext for fighting.