A second fundamental tenet of Christian just war theory is that peace is the natural and desirable state for human beings and that the sole aim of just war is “a certain earthly peace.” (Augustine, City of God, XIV.4) Statecraft that regards war as nothing more than a gambit in the great game of geopolitics or a tool of national power is unjust and immoral.
The Times article quotes National Security Advisor Thomas Donilon’s view that Obama is “a president who is quite comfortable with the use of force on behalf of the United States.” By contrast, just war theory is not comfortable with the use of force, and regards it as at best a necessary evil. As for the view that combativeness is part of human nature, like head-butting among rams, Augustine would concede it only because we are fallen, sinful creatures. In his view, “if the earthly city observes Christian principles, even its wars will be waged with the benevolent purpose that better provision might be made for the defeated to live harmoniously together in justice.”
From David Luban’s “What Would Augustine Do?: The President, Drones, and Just War Theory”