The Christian in Combat

Just war theory is not a fundamental concern of the private citizen or even of the Christian soldier. What is the Christian soldier's concern has to do with just and unjust orders. The Christian may serve in the armed forces of his nation, but he never parks his conscience at the door once he becomes a soldier. It is the Christian's duty to disobey an unlawful order, but may a Christian soldier ever use deadly force to prevent an unlawful order from being carried out?