Science Fair Project Encyclopedia A just war describes a war
that satisfies a set of moral or legal rules. Though in origin a
Catholic doctrine, Francisco de Vitoria based his arguments on
reason and so put the tradition on a more universal basis.  The
rules applied may be ethical, religious, or formal (such as
international law). The rules classically cover the
justification for the war (Jus ad Bellum) and the conduct of the
participants in the war (Jus in Bello). Just war theory has
ancient roots. Cicero discussed this idea and its applications.
Augustine of Hippo and Thomas Aquinas later codified a set of
rules for a just war, which today still encompass the points
commonly debated, with some modifications. In modern language,
these rules hold that to be just, a war must meet the following
criteria before the use of force: (Jus ad Bellum) - War can only
be waged for a just cause, such as self-defense against an armed
attack. - War can only be waged under legitimate authority.
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