Criteria for a Just War

Military action shouldn’t be taken unless it meets all the criteria for a just war; non-violence is preferable but not always appropriate.

The Internet Encyclopedia of Philosophy entry on Just War Theory records a long history of writing on the subject, from Thomas Aquinas onwards.  Robert Skidelsky’s article, The just war tradition, included a historical overview, a definition with clarification, a review of the role of the UN and a brief survey of contemporary issues to which the theory might be applied.  It described ‘just war theory’ in these terms:

“Today, a rich and sophisticated discussion over centuries is usually presented as a list of propositions covering three topics – jus ad bellum, jus in bello and jus ad pacem.  The first aims to determine whether a war is justly started, the second is concerned with the just conduct of the war, and the third – and most shadowy – explores the conditions of a just peace.  The propositions support each other, like bricks in an arch.

…The requirements for a just war are traditionally reduced to six: just cause, legitimate authority, last resort, proportionality between offence and response, reasonable chance of success and right intention.”

In the terminology of this book, these requirements belong to different dimensions of power:

●  “Just cause”, “proportionality”, and “right intention” appear to be moral criteria. People’s assessments will depend on their beliefs.

●  “Legitimate authority” is a legal criterion.

●  “Last resort” is a judgement as to whether both legal and political means have been exhausted.

●  “Reasonable chance of success” appears to be mostly a military judgement, which is classified as Ungoverned Power in this book because it lies outside the four dimensions of structured governance. The question of whether a lasting peace can be achieved, though, also requires a political assessment.

As Skidelsky commented, the propositions of ‘just war theory’ “support each other, like bricks in an arch”.  No-one will accept that a war is ‘just’ unless they think that all the criteria are satisfied, though most people will rely upon the advice of others in the legal, political and military aspects.  The application of ‘just war theory’ was changed by the establishment of the UN, and it needs to evolve further as a result of changes in the military environment, as examined in later chapters:

●  A humanitarian intervention to prevent genocide might be thought to be both a “just cause” and “right intention”, for example, but “legitimate authority” is also needed. The UN Security Council is the only body which can legalise the use of military force (  Several countries contributed to the use of force to drive Saddam Hussein out of Kuwait, for example, in a demonstration of the effectiveness of a rules-based world order (

●  Legality and good intentions do not make an action prudent or beneficial to those affected. Chase Madar wrote, in an article Libyan War: Legal, Multilateral, and Still Wrong, that “[w]hatever value we attach to legality, it is never a proxy or substitute for prudence, good sense or morality”.  The Libyan intervention turned into a disaster when it turned into an attempt to force a regime change (

●  Formal arbitration can be sought, as a form of due process. “Last resort” depends upon whether a dispute had been submitted to an international court (, whose rulings might also be seen as validating some types of “just cause”.

●  “Proportionality” can be taken as requiring a minimum loss of life in achieving the objective.

●  Chances of success must take account of shifting geopolitical alliances: ‘realpolitik’ (

●  The Geneva Conventions cover jus in bello, legally prohibiting avoidable harm to non-combatants ( This has become more complicated when wars are conducted where civilians are living and not on a remote battlefield (

●  The requirements for a just peace, jus ad pacem, include ensuring that the defeated party accepts the result. This depends upon some form of reconciliation. The establishment of the European Union after the Second World War was an outstanding example of a reconciliation that was achieved by political negotiation and which accorded dignity to both sides (6.6.5).  An imposed settlement without agreement can only suppress the confrontation until the balance of power changes again (7.4.5).

For this chapter, the question is whether people as individual moral agents are persuaded that a war is ‘just’.  People can put pressure on politicians if they think that a proposed war would be unjust.  There were public demonstrations of opposition to the invasion of Iraq in 2002 for example, in what the BBC described as a ‘Million’ march against Iraq war, although the politicians ignored them on that occasion.  People’s political support, or lack of it, ultimately limits the use of war as an instrument of policy (6.3.6).

People can also react against misbehaviour and atrocities in the conduct of a war, as reported for example in a BBC article: Picture power: Vietnam napalm attack, which showed a photograph of a little girl running away from a US chemical weapon attack.  The anti-war protest movement gathered momentum and politicians were unable to ignore it.  An estimated 2 million people went on what a BBC retrospective report described as 1969: Millions march in US Vietnam Moratorium.



This page is intended to form part of Edition 4 of the Patterns of Power series of books.  An archived copy of it is held at https://www.patternsofpower.org/edition04/4355c.htm.