The tenth century was a time of change in the common attitude of Christians towards war; a change in fact so great as to be best understood as a swing from one extreme to another, and we should therefore have in mind from the outset two diametrically opposed points of view.
On the one hand, there is the uncompromising rejection of war and of military service by the early Christians. In the first two centuries after Christ, there was virtually no possibility of Christian participation in worldly conflicts between states. The militia Christi, the soldiers of Christ, were always contrasted with the militia saecularis, the soldiers of the world. The soldiers of Christ were to fight a spiritual battle with spiritual weapons, and the final victory was the victory of the martyr; the soldiers of the world fought with carnal weapons for base material ends, and were subject to the lusts of the flesh; there was nothing m common between the camp of light and the camp of darkness.