Ethics of War and the Just War Tradition

1.1 What are the two questions?

Just war thinking asks two separate questions. The first is about going to war. The Latin name is jus ad bellum. The second is about how the war is fought. The Latin name is jus in bello.

In our own plain summary, jus ad bellum asks if it is right to go to war. Jus in bello asks if the fighting is done rightly.

1.2 Why keep them apart?

A good cause does not make every act in the war right, and a bad cause does not make every soldier a wrongdoer. The Stanford Encyclopedia says all combatants are morally permitted to target one another, whatever they are fighting for. Civilians may not be targeted.

So the cause of the war and the conduct of soldiers are judged on their own.

1.3 How would it work?

Here is our own example. A state is attacked and fights back. Its cause is just. Then its army shoots civilians. The cause is still just. The conduct is wrong, and it breaks the rules of jus in bello.

1.4 What is the usual mistake?

Students swap the two terms. Remember this: ad bellum is about going to war. In bello is about conduct in war.

2.1 What are the six tests?

Jus ad bellum typically has six principles. The table gives each one in plain words, close to the Stanford Encyclopedia’s own lines.

Lines are paraphrased from the Stanford Encyclopedia of Philosophy entry on war.

2.2 How do you use them?

The six work as a checklist. In our own reading, a war that fails even one test is open to challenge.

2.3 What is the usual mistake?

Each test must be met, because a strong feeling is not a test. The test names the right kind of injury. Others mix up just cause and right intention. A state can have a just cause and still use it as an excuse for a wrongful end.

3.1 What are the three rules?

• Discrimination: fighters must tell military targets from civilians. They may intentionally attack only military objectives.
• Proportionality: foreseen but unintended harms must be proportionate to the military advantage achieved.
• Necessity: the least harmful means feasible must be used.

3.2 What is double effect?

The doctrine of double effect says it is sometimes permissible to cause a harm as an unintended and merely foreseen side effect. The agent may not positively will the bad effect. The agent may permit it.

3.3 How does it work for bombers?

The Stanford Encyclopedia gives two bombers. The terror bomber aims at civilian deaths to weaken the enemy’s resolve. Those deaths are intended. The tactical bomber aims at military targets. Civilian deaths are foreseen but not intended.

Even if both cause the same number of deaths, terror bombing is impermissible. Tactical bombing is permissible.

3.4 What is the usual mistake?

Students think double effect excuses any civilian death. It does not. The harm must be unintended and merely foreseen. Jus in bello also demands that it stay proportionate.

4.1 Who built the tradition?

The Internet Encyclopedia of Philosophy says Thomas Aquinas gave the most systematic exposition in the Western tradition. He did so in the 13th century.

4.2 What did Aquinas require?

In the Summa Theologiae, he says three things are necessary for a just war.

• The authority of the sovereign, by whose command the war is waged.
• A just cause. Those attacked deserve it on account of some fault.
• A rightful intention. The aim is to advance good or avoid evil.

4.3 What came later?

Hugo Grotius’s De iure belli ac pacis was published by a Paris press in 1625. Michael Walzer’s Just and Unjust Wars was first published in 1977.

The Stanford Encyclopedia calls Walzer’s book extraordinarily influential. Readers include philosophers, political scientists, international lawyers and military practitioners.

4.4 What is the usual mistake?

Students date the whole tradition to Walzer. The book is from 1977. Aquinas wrote six centuries earlier.

5.1 Who are the two camps?

Contemporary just war theory is dominated by two camps. They are the traditionalists and the revisionists.

Both rows are close to the Stanford Encyclopedia’s wording.

5.2 What do traditionalists say about soldiers?

Civilians may not be targeted. All combatants, whatever they fight for, are morally permitted to target one another. That is true even when doing so foreseeably harms some civilians.

5.3 What is the usual mistake?

Students say a soldier on the unjust side commits a crime by fighting. On the traditionalist view, they do not. Revisionists challenge this view.

6.1 What does Article 2(4) say?

Members shall refrain from the threat or use of force against the territorial integrity or political independence of any state. The ban also covers any other manner inconsistent with the Purposes of the United Nations.

6.2 What does Article 51 add?

Nothing in the Charter impairs the inherent right of individual or collective self-defence if an armed attack occurs against a Member. The right lasts until the Security Council has taken the measures needed to keep peace.

Measures taken in self-defence must be reported immediately to the Security Council.

6.3 What can the Council do?

Under Article 42, the Security Council may take action by air, sea or land forces. It may do so to maintain or restore international peace and security.

6.4 How does this link to just war ideas?

This is our own reading. Article 51 matches the just cause of defence. The Council’s role matches the test of legitimate authority.

6.5 What is the usual mistake?

Students mix up Article 2(4) and Article 51. Article 2(4) bars force. Article 51 protects self-defence after an armed attack.

7.1 What is a supreme emergency?

It is a rare case where the usual rules give way. Walzer’s idea covers rare circumstances. In them, intentionally killing noncombatants is necessary to avert an unconscionable threat. The Stanford Encyclopedia gives one example: an imminent catastrophe on the order of Nazi victory in Europe.

7.2 How often does it apply?

Very rarely, because the threat must be unconscionable. Outside such cases, noncombatants may be killed only unintendedly. Even then the harm must be necessary and proportionate.

7.3 What about new weapons?

Recent work looks at drones. It also looks at the possible development of autonomous weapons systems.

7.4 What is the usual mistake?

Students think a supreme emergency allows any harm to civilians when a state is losing. It covers only rare cases that avert an unconscionable threat.

8.1 What did leaders accept in 2005?

The 2005 World Summit Outcome Document carries the Responsibility to Protect, or R2P. Paragraph 138 says each State has the responsibility to protect its populations from genocide, war crimes, ethnic cleansing and crimes against humanity.

8.2 What about other countries?

Paragraph 139 gives the international community a part. Through the United Nations, it has the responsibility to use appropriate diplomatic, humanitarian and other peaceful means to help protect populations.

8.3 When may action follow?

Leaders declared they were prepared to take timely and decisive action. It must be in accordance with the UN Charter. This applies when national authorities manifestly fail to protect their populations.

8.4 What is the usual mistake?

Students call R2P a licence to invade. The text puts peaceful means first. Action must follow the Charter.

9.1 What did the Security Council do?

On 25 February 2022, Russia vetoed a Security Council draft resolution. The draft would have condemned the Russian Federation’s aggression against Ukraine. It was the third emergency meeting on Ukraine that week.

9.2 What did the General Assembly do?

On 2 March 2022 the General Assembly passed a resolution on Ukraine. 141 Member States voted yes and 5 voted no. Ninety-six countries co-sponsored it.

The resolution needed two-thirds of the yes and no votes. The five against were Russia, Belarus, North Korea, Eritrea and Syria. It demanded that Russia immediately withdraw its forces and abide by international law.

9.3 What did the ICC do?

The International Criminal Court opened its investigation in Ukraine on 2 March 2022. Ukraine was not a State Party at first. It twice accepted the Court’s jurisdiction by declaration. It ratified the Rome Statute on 25 October 2024. That took effect on 1 January 2025.

On 17 March 2023, Pre-Trial Chamber II issued warrants for Vladimir Putin and Maria Lvova-Belova. The warrants are for the war crime of unlawful deportation of children.

9.4 What does this show?

In our own reading, the veto shows how the Council can be blocked. The Assembly vote shows a wide majority. The ICC warrants show the law of conduct being applied to named people.

10.1 What did UPSC ask in 2022?

Here is our own plan for the answer. Split it into two parts. First, test the launch of the war against the six jus ad bellum tests. Second, test the fighting against the three jus in bello rules.

10.2 Which numbers should you keep?

• 2: jus ad bellum and jus in bello.
• 6 tests before war and 3 rules in war.
• 1625 Grotius, 1977 Walzer, 2005 R2P.
• Article 51 self-defence. Article 2(4) bars force.
• 141 to 5 on 2 March 2022.