introducing: the "Peace of God" which prohibited attacks on clergy, pilgrims, townspeople, peasants and property; the "Truce of God" which banned warfare on Sundays, Fridays, Lent, and Easter; and it imposed heavy penances on soldiers for killing and injuring others because it believed that the shedding of other people's blood was the same as shedding the blood of Christ. During the 9th and 10th centuries, multiple invasions occurred in some regions in Europe and these invasions lead them to form their own armies in order to defend themselves and by the 11th century, this slowly lead to the emergence of the Crusades, the concept of "holy war", and terminology such as "enemies of God". By the time of the Crusades, "Despite all the violence during this period, the majority of Christians were not active participants but were more often its victims" and groups which used nonviolent means to peacefully dialogue with Muslims were established, like the Franciscans. Today, the relationship between Christianity and violence is the subject of controversy because one view advocates the belief that Christianity advocates peace, love and compassion despite the fact that in certain instances, its adherents have also resorted to violence. Peace, compassion and forgiveness of wrongs done by others are key elements of Christian teaching. However, Christians have struggled since the days of the Church fathers with the question of when the use of force is justified (e.g. the Just war theory of Saint Augustine). Such debates have led to concepts such as just war theory. Throughout history, certain teachings from the Old Testament, the New Testament and Christian theology have been used to justify the use of force against heretics, sinners and external enemies. Heitman and Hagan identify the Inquisitions, Crusades, wars of religion, and antisemitism as being "among the most notorious examples of Christian violence". To this list, Mennonite theologian J. Denny Weaver adds "warrior popes, support of capital punishment, corporal punishment under the guise of 'spare the rod spoil the child,' justifications of slavery, world-wide colonialism under the guise of converting people to Christianity, the systemic violence against women who are subjected to the rule of men." Weaver employs a broader definition of violence that extends the meaning of the word to cover "harm or damage", not just physical violence per se. Thus, under his definition, Christian violence includes "forms of systemic violence such as poverty, racism, and sexism". Christian theologians