Luke 12:39 and Matt. 25:43 "But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up."
You cannot find any evidence in the NT that killing or murder was accepted. For when Peter tried to cut the ear off the soldier, Jesus put it back on, and told him to put his sword up. You can find no other mention in the NT about standing up to the political system of the day, at all, other than the two verses I mention above.
So I think that as long as we are defending our home, and our families, it seems that it would be okay to take defensive action, if there is no other way.
Regarding defending one's country, again, as you see all throughout the OT that is expected of a man, but in the NT, there is no mention of any of the apostles, or disciples of Jesus defending Israel or partaking in any kind of Roman army position or opposition.
So, the rational thing to conclude would be that Jesus ushered in a new kingdom of love at Calvary, and that meant loving your enemies, and doing good to those that despitefully used you; yet according to the two scriptures above, it does seem that protecting your home, and those you love against the thief and robber were expected of a man.