Under ''jus ad bellum'', only legitimate authorities can wage war for the right reasons (usually this means a defensive war, or a war of defending the weak against a violent oppressor <ref>[http://biblehub.com/proverbs/24-11.htm Proverbs 24:11] and [http://biblehub.com/commentaries/proverbs/24-11.htm commentaries]; see also [http://biblehub.com/psalms/82-4.htm Psalm 82:4] and [http://biblehub.com/job/29-17.htm Job 29:17].</ref>) and only as a last resort if every other peaceful means to avert war have been used to no avail. A just war can only be waged if there is a serious evil that needs to be stopped. Further there must be a realistic chance that the evil can be stopped without starting a greater evil. If this happens the war reaches a just conclusion. A war started for just reasons and justly waged may still reach an unjust conclusion.
<br />[[File:Saint Augustine by Philippe de Champaigne.jpg|rightcenter|thumbnail|300px|St. [[Saint Augustine]] ]]
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