What are religious beliefs in the 19th centuries of religion? Wars between Christians and non-cruises, civil wars in which the border between friends and enemies or between soldiers and simple subjects is fading, a dramatic combination of urban riots, peasant revolts, uprisings against new forms of power and brutal massacres more often than military military operations in good order, they blurred the tracks, defeat too simple interpretations, and raise countless questions. In order to understand its deep originality and the decisive role in the birth of modern Europe, it is therefore necessary to cross-check several analyses: a comparative history of wars in different territories in order to grasp their specific national or faith-based characteristics; a study of the various actors and the justifications they give to their involvement in war or peace; finally, a detailed description of the specific forms of violence that can be observed. It is this challenge that the book seeks to address by choosing a European perspective and novel documentation, since, like humanism and Renaissance, but on a completely different, more worrying register, the religious clashes of the 16-17th centuries may be the crucible from which modern Europe has emerged.