“Does loving your enemy mean not punishing him? No, for loving myself does not mean that I ought not to subject myself to punishment–even to death. If one committed a murder, the right Christian thing to do would be to give yourself up to the police and be hanged. It is, therefore, in my opinion, perfectly right for a Christian judge to sentance a man to death or a Christian soldier to kill an enemy. I always have thought so, ever since I became a Christian, and long before the war, and I still think so now that we are at peace. It is no good quoting “Thou shalt not kill.” there are two Greek words: the ordinary word to kill and the word to murder. And when Christ quotes that commandment He uses the murder one in all three accounts, Matthew, Mark, and Luke. and I am told there is the same distinction in Hebrew. All killing is not murder any more than all sexual intercourse is adultery. When soldiers came to St. John the Baptist asking what to do, he never remotely suggested that they ought to leave the army: nor did Christ when he met a Roman sergeant-major–what they call a centurion. The idea of the knight–the Christian in arms for defence of a good cause–is one of the great Christian ideas. War is a dreadful thing, and I can respect an honest pacifist, though I think he is entirely mistaken.
C S Lewis, Mere Christianity