The Bible tells us that God has given the State (legitimate government) the right and responsibility to bear the sword of steel (protect the righteous (the law-abiding) and to punish the wicked (the lawbreakers). This includes military as well as civil action. In the days of Noah, God gave this authority to the State (not the Church or individual Christians). There is a Divine distinction between worldly authority and spiritual authority. Since the State has this Divine responsibility, it is consistent for Christians to support the State's responsibility through taxes spent on law and order.
I know some folks don't agree that believers and the Church are not subject to the State concerning the use of deadly force. We are told to submit to legitimate authority, but we are also told, when the State requires something from us, "we must obey God rather than men."
I did a New Testament search of verses, which folks use to "prove" the false notion that Christians can use lethal force, either for national defense, civil order, or self-defense. In the New Testament, God never commands, commends, or condones Christians or the Church to take up arms against any other person or to use deadly force. In fact, God condemns the use of such force in the New Testament by His people.
The few verses that are used in the New Testament are totally unrelated to this issue. In fact, they cannot be considered as serious arguments.
So, why do "Chirstian" people think that the New Testament teaches Christian violence? It is because Roman Catholic beliefs, rooted in paganism during the days of Constantine (early 300s), were adopted by the Protestant Reformers in the 1500s and they have been passed on to various groups for the past 500+ years. For the first 300 years of the Church, Christian non-violence was the understood standard. Through the centuries various "back to the Bible" groups recognized the Biblical teaching of non-violence and the major portion of those who call themselves Bible believing Christians have understood the New Testament teaching. In fact, even the unsaved world has viewed and accepted that Christianity followed the teachings of Christ and the New Testament by practicing non-violence.
In recent years there has been a resurgence of Reformed and Calvinistic teaching that embraces "Christian violence."
If you have questions about this subject, I will be glad to look at New Testament teaching with you.