Violence is a tool. It is not a hammer or screwdriver that goes in your toolbox for everyday use. It is a tool of last resort. It is behind the glass broken only in extreme circumstances. What are the appropriate circumstances? We always want to avoid violence but there are circumstances when violence is necessary.
The Qur'an and hadiths of Islam teach that violence is an appropriate tool for the propagation of religion. In contrast, the Hebrew conquest of Canaan was a period in which God-ordained violence occurred but the purpose of the conquest was not to gain converts. Later, Jesus and the entire New Testament make it very clear that violence must never be a tool for the Church to spread Christianity or the gospel message. This brings us to the question of self-defense.