Duhaime's Law Dictionary

Just War Definition:

A war which is primarily defensive or retributive.

Related Terms: War

A species of war mused about by legal philosophers which allowed for the legitimization of the military exercise and especially of the conquest of land by that country purporting to exercise a just war.

St. Augustine wrote, in Concerning the City of God Against the Pagans, of the Roman Empire in the following words often used to explain the concept of a just war:

"... to rejoice in the extent of empire is not a characteristic of good men. The increase of empire was assisted by the wickedness of those against whom just wars were waged. The empire would have been small indeed, if neighbouring peoples had been peaceable, had always acted with justice, and had never provoked attack by any wrong-doing. In that case, human affairs would have been in a happier state ...

"To make war and to extend the realm by crushing other peoples, is good fortune in the eyes of the wicked; to the good it is stern necessity... It is a wicked prayer to ask to have someone to hate or to fear, so that he may be someone to conquer."

just war greeting signThe distinctions of a just war as opposed to war, are legion in the dusty pages of ancient legal books as one can well imagine, mostly so justify the acquisition of territory by conquest. Australian Gavin Loughton wrote, in his 2004 article:

"Canon law allowed that there could be a just war. Indeed that this was the only kind of war that canon law would recognise as having legal standing.

"(English author) Maurice Hugh Keen, in his discussion of the law of war in the late middle ages, notes something equally true of the period of interest to us: 'The first principle of the legists was that only a just war could have legal consequences'.

"A just war is not the same as conquest .... The just war is primarily defensive or retributive, not aggressive.

"The influential canon lawyer Gratian (writing c. 1140) synthesized the ecclesiastical authorities into this formula: the just war must be authorised by a legitimate public authority, and be waged in response to some kind of injury: for instance, to recover lost goods, to punish wrongs, or in self-defence. These criteria found their way, by a circuitous route, into Bracton's treatise.

"The civilian jurist Azo (of Bologna), following Justinian, wrote that war could be attributed to the law of nations. But then Azo added something not found in the corresponding passage in the Digest, namely Gratian's limiting criteria for the just war: the wars that are funded on the law of nations (says Azo) are those declared by the prince and/or to repel an attack.

"Bracton reproduced, with only minor alterations, Azo's rendition of the Digest complete with the canon law interpolation.

"Thus the canon law's suspicion of aggressive wars is present in an English law book."


  • Loughton, Gavin, Calvin's Case and the Origins of the Rule Governing Conquest in English Law, 8 Austl. J. Legal Hist. 143 (2004)

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