Thomas Merton was a Trappist Monk. He wrote over sixty books before his death in 1968 including The Seven Storey Mountain, and Peace in the Post-Christian Era, which was not published until 2004. I have been reading the latter and am enjoying it very much. Here are some excerpts:

Christians believe that Christ came into this world as the Prince of Peace. We believe that Christ himself is our peace (Eph. 2:14). We believe that God has chosen for himself, in the Mystical Body of Christ, an elect people, regenerated by the blood of the Savior, and committed by their baptismal promise to wage war upon the evil and hatred that are in man, and help to establish the kingdom of God and of peace.

For he himself is our peace, who has made the two one and has destroyed the barrier, the dividing wall of hostility, by abolishing in his flesh the law with its commandments and regulations. His purpose was to create in himself one new man out of the two, thus making peace, and in this one body to reconcile both of them to God through the cross, by which he put to death their hostility. He came and preached peace to you who were far away and peace to those who were near. For through him we both have access to the Father by one Spirit. -Ephesians 2:14-18

The Christian commandment to love our enemies was not regarded by the first Christians merely as a summons to higher moral perfection than was possible under the Old Law. The New Law did not compete with the Old, but on the contrary fulfilled it, at the same time abolishing the conflicts between various forms of obligation and perfection. The love of enemies was not therefore the expression of a Christian moral ideal, in contrast with Stoic, Epicurean or Jewish ideals. It was much more an expression of eschatological faith in the realization of the messianic promises and hence a witness to an entirely new dimension in man's life... The Christian is and must be by his very adoption as a son of God, in Christ, a peacemaker (Matt. 5:9). He is bound to imitate the Savior who, instead of defending himself with twelve legions of angels (Matt 26:55), allowed himself to be nailed to the Cross and died praying for his executioners.

Jesus said, "My kingdom is not of this world. If it were, my servants would fight to prevent my arrest by the Jews. But now my kingdom is from another place."

"You are a king, then!" said Pilate.

Jesus answered, "You are right in saying that I am a king. In fact, for this reason I was born, and for this I came into the world, to testify to the truth. Everyone on the side of truth listens to me." -John 18:36&37

"You have heard that it was said, 'Love your neighbor and hate your enemy.' But I tell you: Love your enemies and pray for those who persecute you, that you may be sons of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. If you love those who love you, what reward will you get? Are not even the tax collectors doing that? And if you greet only your brothers, what are you doing more than others? Do not even pagans do that? Be perfect, therefore, as your heavenly Father is perfect. -Matthew 5:43-48