Is religion a force for war, or a force for peace? Some of the most terrible wars in history have been caused and motivated by religion. Much of the violence that fills our screens today springs from the same source. Yet some of the bravest pacifists have also been deeply religious people, and many of the laws and institutions that work to soften or prevent war have deep religious roots. This Very Short Introduction provides an overview of the history of religion and war, and a framework for analyzing it. Ranging from the warrior gods of Ancient Greece and Rome, and the ethical drama of the Mahabharata, through the Islamic wars of conquest and the Crusades, to present day conflicts in Sri Lanka and the Balkans, it considers the entanglement of war and religion. Yet from Just War theory and the restraints on war-making imposed by Islamic jurisprudence, through the Pax Christi of the middle ages, to the non-violence of Gandhi and Bacha Khan; there is also a story to be told of peace and religion as well. Jolyon Mitchell and Joshua Rey consider both sides of the age long drama of war and religion, challenging assumptions at the most fundamental level. Throughout, they encourage a more sophisticated and well-grounded view on these issues that have had such weight in the past, and continue to shape our present and future.