Just war theory is constructed in two parts. The doctrine of jus ad bellum determines when it is moral to enter a war. The doctrine of jus in bellum dictates how a war should be conducted during the course of the conflict. There are many different variations on these doctrines, but their overall ideas remain the same and are reflected below.

Jus ad bellum- the guidelines for entering war
1. The authority waging the war must be legitimate. “Even just causes cannot be served by actions taken by individuals or groups who do not constitute an authority sanctioned by whatever the society and outsiders to the society deem legitimate.”
- Currently, a nation-state is the only authority that can wage war. (A nation-state is any sovereign country.)

2. The cause being fought for must be just.
- The only just cause for war is to redress wrongs suffered. It is not just to fight for financial or political gain.

3. The ultimate goal (“intention”) must be peace.
- War cannot continue indefinitely and a just war must have a goal of peace, not continuing terror.

4. The subjective motivation (“intention”) must not be hatred or vengefulness.
-Just war can only be motivated by specific wrongs suffered, not for emotional reasons dealing with the governing bodies. The just war theory prefers a restatement of the status quo at the end of the conflict and not an intended shift in power.

5. War must be the last resort.
- Before choosing to go to war, all other attempts at peace must be exhausted. War can only be just when every other conceivable option has been tried and failed. This includes the application of trade embargos, diplomatic visits, and the intervention of peace-keeping organizations like the UN.

6. Success must be probable.
-If a war cannot bring about success and eventual peace, it cannot be just. Even an attempt at war must have a chance of success. A war that is unsuccessful is more dangerous than an unwaged war, as it has a higher account of death and destruction. Morally, it is better not to go to war at all if you’re not sure there is a chance you can win.

Jus in bellum- guidelines for fighting a war
1. The means used must be indispensable to achieve the end.
-Every action must have no alternative and must add to the progression of the war, leading towards the end and peace.

2. The means used must be discriminating:
a. Quantitatively, in order not to do more harm than the harm they prevent (“proportionality”)
-It is necessary to keep track of the casualties inflicted by war and weigh them against a hypothetical situation in which the war had not taken place and the initial problems continued. This must be done constantly, with attention paid to ensure that everything is being done to make things better, even for the time being.
b. Qualitatively, to avoid use against the innocent (“immunity”)
-The death of non-combatants violates the doctrine of just war. Weapons used must be able to distinguish between combatants and innocents. It is vital that the rights of the innocent are protected to make a war qualify as “just”. The classification falls away when there is no distinction between innocent citizens and the military opponent in a given situation.

3. The means used must respect the provisions of international law.
-This includes those laws laid out at the Geneva Convention. Principles of humanity must be adhered to, with captured enemy combatants safe from torture. In a just war, prisoners of war are entitled to humane treatment. The torture or maltreatment of prisoners would conflict with the other principles of just war, like the concept of only using procedures that are indispensable to achieve the end. When the enemy has already been captured, their continued torture does not follow this rule.

Basic guideline adopted from: (Yoder, When War is Unjust p.18)