Shortly after the terrorist attack on September 11, the Dorothy Day Catholic Worker House in Washington, D.C., proclaimed, “If we kill as a response to this great tragedy, we are no better than the terrorists who launched this awful offensive. Killing is killing, and killing is wrong.”

Not only pacifists but also moderates seem to share this basic view. Theologian Miroslov Volf, while acknowledging the justness of a military response to the attack on the U.S., also said, “Taking a life is always the wrong thing.”

Yet few people are aware of what a stunningly new thing this is—for Christians of all stripes and backgrounds to eschew all violence. Disillusionment with the military after Vietnam surely contributed to it, as has a growing repugnance for suffering, blood, and death in our antiseptic culture. But two historical assumptions seem to drive many believers’ thinking on this matter.

The first assumption is that the New Testament is uniformly against violence. In The Moral Vision of the New Testament, pacifist Richard Hays utters something many nonpacifists affirm: “From Matthew to Revelation, we find a consistent witness against violence and a calling to the community to follow the example of Jesus in accepting suffering rather than inflicting it.”

It’s a sweeping sentiment that, it turns out, sweeps too broadly. When John the Baptist told soldiers to repent, he did not ask them to forsake their professions. He simply told them to soldier with integrity. When Jesus meets a Roman centurion, far from commanding him to give up his calling, he praises the man for his great faith. When Roman commander Cornelius becomes a Christian, he is not told in his dreams or by the apostles that laying down his arms is a ...