The Crusades in Europe: The History of the Catholic Crusaders' Campaigns against the Ottomans and Christians across the Continent

Christianity was not a state religion for its first three centuries, and it was only when Emperor Constantine the Great declared it so in the early 4th century that the Church was faced with the thorny problem of state-sanctioned violence. The first major Christian authority to justify the use of arms in defense of Church and State was Augustine, Bishop of Hippo, who wrote in the 5th century, “They who have waged war in obedience to the divine command or in conformity with His laws, have r...