Rules of a Just War

Peace and War

What is a "Just War"?

"Just War" is a theory that is used to justify wars and also limit them.

The theory was developed by St. Augustine. He developed the theory because of his anxiety over the fate of the Christian Empire, and his belief that the common good must be upheld. The theory is sometimes referred to as approval of war. Augustine drew his ideas from the idea that war must be fought for the common good, not for an individual.

St. Thomas Aquinas further elaborated on the conditions of a "Just War" that were developed by St. Augustine. He elaborated on the first condition, that there must be a legitimate authority to proclaim war, and the second condition, that combatants must avoid civilian causalities and limit the amount of forced used to the minimum required and that prisoners must be treated humanely.

The Rules of a Just War.

The rules of a "Just War" are:

1 - The war must be started and controlled by a lawful authority.

2 - There must be a just reason for war.

3 - The war must be the last resort, used after all other options have been attempted.

4 - The war must be used for good and not evil causes.

5 - Proportionality, that is, only a necessary amount of force is to be used to achieve peace.

6 - There must be a reasonable chance of winning war.

Examples of "Just Wars".

Some people believe that World War II was a "Just War" in the case of the Allies as they were defending themselves and others from the Germans.

Others may say that the Gulf War was also a "Just War". It started in response to Iraq's invasion of Kuwait.

Other Information.

A "Just War" ceases to be a "Just War" when:
  • Innocent people and those who are not involved in the fighting, are harmed.
  • More force than necessary is applied during combat, this includes the type of force and how much of it is used.
  • Internationally agreed upon laws regarding war are breached.

References / Bibliography.


Red, War and Peace Booklet distributed in class.

BBC - Ethics - War: What is a Just War? n.d., BBC <>

Gulf War 26 August 2013, Wikipedia, <>

Englebretson , K., Duncan, B., Elliot, P. J., Rule, P., Rymarz, R. 2004 To know, worship and love - Catholic ethical thinking for senior secondary students


WST School Tours | Religion Studies at The WW1 Battlefields, n.d., WST, <>

(Re)Living the Civil War | TriMadness! 8 February 2013 TriMadness! <>

By Jennifer Laan