The second clause is “the cause of the war must be just”. St Augustine believed that there were only three just causes:
- defending against attack
- recapturing things taken
- punishing people who have done wrong
These are all just because they deserve to be harmed because they have done wrong.
The third clause “the war must be fought with the intention to establish good or correct evil”, this means that there has to be good intentions like creating, restoring or keeping peace, righting a wrong or assisting the innocent, not for reasons such like gaining power or hatred of the enemy. A Bible teaching that supports this clause is Matthew 5:38-39 It says that you should not take revenge, this relates because it is a poor reason to go to war and is not a just cause.
The fourth clause “there must be a reasonable chance of success”, means that it is wrong to go to war if you do not have good chance of winning. It is considered unethical to go to war with no chance of victory because it is a waste of your men’s life and your enemies men’s life. I couldn’t find any church teachings that support this clause, but if you look at it from an ethical perspective you can see that there is clear reasoning behind it.
The fifth clause “the war must be the last resort” this means that all diplomatic negotiations etc. have been tried and have failed. This has to be the case because the intention of war has to be to make peace. A bible teaching that supports this clause is Matthew 5:25, “If someone brings a lawsuit against you and takes you to court, settle the dispute with him while there is time, before you get to court.” This to me says that every possible mean of prevention and negotiations must be tried before you go to war.
The final clause “The war must be in proportion”, this means that it must prevent more evil than it causes and it must prevent more human suffering than it causes. One church teaching that loosely supports this clause is in the catechism of the catholic church number 2308 it says that a country can lawfully go to war in self defence.