Explanation: Romans placed a relatively high value on the idea of bellum iustum - ‘justified war’, rather than just conquering their enemies to hear the lamentations of their women and all that jazz. On one hand, this is a very good and civilized thing, to demand of oneself justification for acts of violence, a step, however small, in the right direction.
On the other hand, as the Romans were a very warlike people, this meant that Rome was generally eager to pounce on any slight that could give them a justification for intervening and putting yet another province under their heel. Raid a ‘friend of Rome’? Full-scale war. Mistreat a Roman citizen? Full-scale war. Technical violation of some minor clause of the last peace treaty you signed? Oh, you better believe that’s full-scale war.