Just war
The concept of a just war is old. as long ago as ancient Egypt the concept existed although it was presented as a divinely ordained act. All civilisations have wrestled with the moral question of when is it justified to kill others and destroy what people have made to support their lives.
The Hindu epic the Mahabharata dating from the 4th century BCE has a discussion of proportionality (chariots cannot attack cavalry, only other chariots; no attacking people in distress), just means (no poisoned or barbed arrows), just cause (no attacking out of rage), and fair treatment of captives and the wounded.
One of the most significant figures to consider the justification of war is Augustine of Hippo, the north African theologian and philosopher (4 to 5th C). Other significant western philosophers to contribute to the development in western European societies are Thomas Aquinas, a Dominican friar (13th C), and Hugo Grotius, a Dutch jurist (16 to17th C).
The following criteria can be used to decide whether a war is just:
Authority for the war - is the authority waging the war properly founded and supported by the people on whose behalf the war is being fought?
Reason for war - is the aggression which is the occasion of the war sufficient to justify killing people?
Proportionality - are the weapons and their effects proportionate to the weapons used to attack?
Combatants - does the war restrict, as much as is possible, the effects of its actions to combatants, that is not harm civilians, including children?
Result of war - is there a clear and likely achievable result of the war?
Last resort - have all other means, such as diplomacy, been used to avoid the war?
1992 Catechism of the Catholic Church, in paragraph 2309, lists four strict conditions for "legitimate defense by military force:"
- The damage inflicted by the aggressor on the nation or community of nations must be lasting, grave and certain.
- All other means of putting an end to it must have been shown to be impractical or ineffective.
- there must be serious prospects of success.
- The use of arms must not produce evils and disorders graver than the evil to be eliminated.
Further reading
The Bhagavad Gita and the Ethics of War
Sources:
Wikipedia
A Level Philosophy Michael Lacewing