The Huguenots where Calvinist French Protestants who spread the religion into northern France, they were hunted down by the Catholics in order to stop them. Nowadays that seems extremely silly but worse things have happened for less with religion, I mean the 30 years war was a big one, the crusades started when the Byzantine emperor felt threatened by Islam invaders(the crusades evolved into taking the holy land back later) and the holocaust all happened because of religion. It’s not just these events that happened because of religion, just some of the notable ones.