A - Thanks for the great question. Let us first look at a few pertinent passages from Scripture and from the Catechism of the Catholic Church.
"You have heard that it was said, 'You shall love your neighbor and hate your enemy.' But I say to you, love your enemies, and pray for those who persecute you" - Matt 5: 43-44In this passage, Christ is teaching that there is a new depth to the commandments that we must obey. It isn't just the letter of the law, but the spirit we are called to.
The Catechism says this about war:
2263 The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing. "The act of self-defense can have a double effect: the preservation of one's own life; and the killing of the aggressor. . . . The one is intended, the other is not."It then says:
2264 Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one's own right to life. Someone who defends his life is not guilty of murder even if he is forced to deal his aggressor a lethal blow:We have a duty to protect our country in a just war and this may mean that we have to take the lives of others. The question remains - is this love? I say it is. Love is not always "nice". In the case of a just war, the loving act is to defend your nation. I commonly define love as = "choosing what is best for another, despite the cost to myself". I believe this kind of love can be practiced, even in war.
If a man in self-defense uses more than necessary violence, it will be unlawful: whereas if he repels force with moderation, his defense will be lawful. . . . Nor is it necessary for salvation that a man omit the act of moderate self-defense to avoid killing the other man, since one is bound to take more care of one's own life than of another's.
2265 Legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm. For this reason, those who legitimately hold authority also have the right to use arms to repel aggressors against the civil community entrusted to their responsibility.
CS Lewis comments on this line of thought in the great book, Mere Christianity.
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 you had 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 sentence 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.He then goes on to say:
We may kill if necessary, but we must not hate and enjoy hating. We may punish if necessary, but we must not enjoy it… Even while we kill and punish we must try to feel about the enemy as we feel about ourselves – to wish that he were not so bad, to hope that he may, in this world or another, be cured: in fact, to wish his good. This is what is meant in the Bible by loving him: wishing his good, not feeling fond of him nor saying he is nice when he is not.There can be legitimate differences of opinion on this issue. Some Christians have practiced pacifism as a Christian lifestyle. But, what we ought not do is tell someone else they cannot have a differing opinion once we act with an informed conscience on this issue. What we should all be able to agree with is that peace should be the goal of all.
Click here to learn about Just War Theory.