The Old and New Testament teaching seem in conflict over the use of force. Could you tell me when, if ever, it is appropriate for a believer to use force?
Actually, the teachings about use of force between the Old and New Testaments are not really at odds, but are complimentary, having a different focus on when, where and how. For example, both the Old Testament and New Testament (Romans 13) teach that it is proper to use force for the purpose of restraining evil and wickedness in the world. It is also proper to use force for the defense of a nation. However, the one place it is not permitted to use force is for the defense of the faith. As far as the faith is concerned, we must turn the other cheek and we must be willing to become martyrs. As far as protecting ourselves from crime and protecting our nation from foreign aggression, then force is allowed by both testaments. The Bible does not teach pacifism. Pacifists usually use verses that apply for the defending of the faith, and ignore the context, which has nothing to do with defenses against evil doers and against national aggression.