Understanding the Just War Theory

These criteria (jus ad bellum), taken as a whole, must be satisfied in order to override the strong presumption against the use of force.

Just Cause

Force may be used only to correct a grave, public evil, i.e., aggression or massive violation of the basic rights of whole populations.

Comparative Justice

While there may be rights and wrongs on all sides of a conflict, to override the presumption against the use of force the injustice suffered by one party must significantly outweigh that suffered by the other.

Legitimate Authority

Only duly constituted public authorities may use deadly force or wage war.

Right Intention

Force may be used only in a truly just cause and solely for that purpose.

Probability of Success

Arms may not be used in a futile cause or in a case where disproportionate measures are required to achieve success.

Proportionality

The overall destruction expected from the use of force must be outweighed by the good to be achieved.

Last Resort

Force may be used only after all peaceful alternatives have been seriously tried and exhausted.

The just-war tradition seeks also to curb the violence of war through restraint on armed combat between the contending parties by imposing the following moral standards (jus in bello) for the conduct of armed conflict:

Noncombatant Immunity

Civilians may not be the object of direct attack, and military personnel must take due care to avoid and minimize indirect harm to civilians.

Proportionality

In the conduct of hostilities, efforts must be made to attain military objectives with no more force than is militarily necessary and to avoid disproportionate collateral damage to civilian life and property.

Right Intention

Even in the midst of conflict, the aim of political and military leaders must be peace with justice, so that acts of vengeance and indiscriminate violence, whether by individuals, military units or governments, are forbidden.