International humanitarian law, or jus in bello, has its foundations in the thoughts of thinkers such as Thomas Aquinas, Aristotle, Plato, as well as many more. It is the law that governs the way in which states conduct warfare in an attempt to make it less violent and as morally acceptable as possible. These ideas became the foundations of international law, as their philosophy is present in various famous international treaties such as the Treaty of Versailles, the 1856 Paris Declaration on Maritime Warfare, and the Geneva Convention.
Jus in bello, when combined with jus ad bellum (the conditions under which waging war is acceptable), attempts to limit the violence and number of wars and has many significant demands in order to ensure that a war between states is just.
The first is that states must identify who and what are legitimate targets during war. The second is that actions in war must be proportional to the actions of opponents, that military action should be proportional to the desired goal, and that weapons capable of damaging both legitimate and illegitimate targets simultaneously are forbidden. The final rule jus in bello advocates is that prisoners of war must be humanely treated and are entitled to basic human rights and respect (Maiese, 2003).
Despite the principles of jus in bello forming many modern understandings of the guidelines of war, there is a doctrine known as the Supreme Emergency (SE) Doctrine that challenges its principles. This is because the SE Doctrine, created by realist thinkers such as John Mearsheimer and advocated for by thinkers such as Winston Churchill and Michael Walzer, argues that constraints on warfare are illegitimate, as there are circumstances in which states are entitled to do whatever it takes to achieve victory. As a result, this doctrine challenges jus in bello in several ways (Walzer, 2015).
The first is that the SE Doctrine argues that if a country’s freedom or existence is under threat, then jus in bello can be ignored. The second is that if a state is not fighting another state, jus in bello does not apply. The final contradiction is that a leader has a greater obligation to the safety of their own people than to prisoners of war or the people of an opponent nation.
As mentioned, the first main principle of jus in bello is that states at war should make a clear distinction between legitimate and illegitimate targets. This is because killing is morally wrong; therefore only targets such as military bases, soldiers, railways, and infrastructure used for the war effort are legitimate.
Soldiers and other war actors have sacrificed some of their basic human rights and safety by inflicting violence on behalf of their state, with many joining voluntarily. Their deaths and the destruction of their equipment can therefore be justified due to their willingness to be put in danger (Maiese, 2003).
Civilians, schools, hospitals, places of worship, and other non-military targets have not surrendered such rights and do not contribute to the war effort, making attacks on them morally indefensible. The doctrine of double effect acknowledges that civilian casualties may occur accidentally during attacks on legitimate targets.
The SE Doctrine argues that there are situations in which jus in bello does not apply, making the bombing of non-combatants legitimate. One such situation is when a state’s culture, people, and way of life face annihilation. Walzer argues that collectives must do whatever it takes to protect individuals from massacre and enslavement (Statman, 2006).
Winston Churchill used this reasoning for the bombing of German civilian targets during the Second World War, believing that as long as Nazism flourished, Europe and the UK could not be free (The Churchill Centre, 2013).
The SE Doctrine also claims jus in bello is outdated because modern wars often involve terrorist organisations rather than states. Terrorist groups blur the line between civilians and combatants, using civilian environments as protection. Thus, civilian targets may be considered legitimate in counterterrorism efforts. Israel’s bombing of hospitals and civilian infrastructure after 7 October follows this rationale (Milanovic, 2023).
Another principle of jus in bello is that states should ensure their retaliations are proportional to the actions of their aggressor and that attacks must be proportional to the intended objective. For example, blockades should cause as little destruction as possible, making the deliberate starvation of civilians disproportionate (Maiese, 2003).
This principle prohibits weapons and tactics that cause escalation or indiscriminate harm, including poison gas, starvation, destruction of essential civilian infrastructure, and environmentally damaging weapons.
The SE Doctrine challenges this principle by arguing that states have a greater obligation to their own citizens’ safety than to enemy civilians. Any means necessary may be used to end a war quickly, as prolonged conflict endangers more people.
This reasoning underpinned the nuclear bombings of Hiroshima and Nagasaki. While jus in bello considers nuclear weapons disproportionate to Japanese aggression and the United States’ war aims, American leaders argued that ending the war swiftly was necessary to protect American lives (Hamby, 2023).
The final principle of jus in bello concerns the humane treatment of prisoners of war. Although soldiers give up some rights by fighting, they do not forfeit all rights permanently. Once surrendered, they become illegitimate targets and must be treated accordingly: their property protected, no torture or intimidation, no forced labour, and basic necessities must be provided (Maiese, 2003).
The SE Doctrine argues that when a state faces threats from non-state actors such as terrorists, jus in bello cannot be upheld. Terrorists are said to be undeserving of the same protections as soldiers from recognised states, having renounced their citizenship and violated international norms.
The doctrine states that a government’s foremost responsibility is to protect its own citizens. As such, the wellbeing of terrorists may not be prioritised. This rationale underpinned President Bush’s establishment of Guantanamo Bay after 9/11 to detain suspected and known terrorists under conditions that contradicted jus in bello. Bush argued that terrorists were undeserving of full protections and that the United States had a moral duty to ensure national security above all else (Quintart, 2016).
Therefore, although jus in bello forms the foundation of modern understandings of what is legal during war through its demand that states distinguish between military and civilian targets, ensure proportionality, and treat prisoners of war humanely, the Supreme Emergency Doctrine disputes these rules. It proposes that situations exist in which jus in bello cannot or should not be followed, particularly when a state faces existential threat or fights non-state actors. It also argues that leaders have a greater obligation to their own citizens than to protecting the rights of their enemies.