Sectarian violence among Christians is a recurring phenomenon, in which Christians engage in a form of communal violence known as sectarian violence. This form of violence can frequently be attributed to differences of religious beliefs between sects of Christianity (sectarianism). Sectarian violence among Christians was common, especially during late antiquity, and the years surrounding the Protestant Reformation, in which the German monk Martin Luther disputed some of the Catholic Church's practices; particularly the doctrine of Indulgences, and it was crucial in the formation of a new sect of Christianity known as Protestantism. During the latter half of the Renaissance was when sectarianism related violence was most common among Christians. Conflicts like the European wars of religion or Dutch Revolt ravaged Western Europe. In France there were the French Wars of Religion and in the United Kingdom anti-Catholic hate was heightened by the Gunpowder Plot of 1605. And while sectarian violence may seem like an archaic footnote today, sectarian violence among Christians still persists in the modern world with groups such as the Ku Klux Klan (which prominently uses the Bible along with the official KKK handbook, the Kloran, to espouse its teachings) perpetuating violence among Catholics.
The earliest period when widespread sectarian violence occurred among Christians was the period of late antiquity (3rd century CE to 8th century CE). Events like the wars which followed the Council of Chalcedon and Constantine's persecution of the Arians caused late antiquity to be considered one of the worst periods of time for a person to be a Christian in. Other conflicts such as the Albigensian Crusade, led to wars with over 1,000,000 casualties.
