“But war is contrary to a Divine precept, for it is written (Matt. 5:39): "But I say to you not to resist evil"; and (Rom. 12:19): "Not revenging yourselves, my dearly beloved, but give place unto wrath." Therefore war is always sinful.
Obj. 3: Further, nothing, except sin, is contrary to an act of virtue. But war is contrary to peace. Therefore war is always a sin.
Obj. 4: Further, the exercise of a lawful thing is itself lawful, as is evident in scientific exercises. But warlike exercises which take place in tournaments are forbidden by the Church, since those who are slain in these trials are deprived of ecclesiastical burial.”