The just war tradition was largely a creation of the medieval Christian Church. Various other cultures like the Greeks, Egyptians, and Romans made contributions. However, the concept was not elaborated on in detail before the great theologians like St. Augustine of Hippo and St. Thomas Aquinas. Their respective works made tremendous progress in giving future generations a standard to start with. Since then, principles have been added, giving the modern world a fertile understanding of what constitutes a just war.
The first principle is that wars must be declared by the appropriate authority. In the United States, the Constitution grants that authority to Congress, not the executive branch of government. As such, President Biden’s recent bombing of Yemen would be deemed both unconstitutional and also unjust because it was waged without the consent of Congress. They would engage in fewer international conflicts if the United States abided by that principle. Perhaps, they need to be reminded that wars waged by inappropriate authority are unjust.
The second principle is that the war must have a just cause. It is not enough for the proper authority to declare war if the war has an unjust cause. This principle can certainly be twisted. Almost all armies will always deem their cause as just. However, Saint Augustine of Hippo provided future generations with a baseline to judge their cause as just or not. First, the war can only be justified by the injustice of an aggressor. Secondly, it must be in the pursuit of peace. Military campaigns waged to expand borders are unjust. Military campaigns waged without the instigation of an aggressor are unjust. Expansionist foreign policy is unjust because it fights uninstigated and without a just cause. “Spreading democracy” to foreign lands that do not want democracy is not a just cause. Unfortunately, that is only expansionism under the false pretense of “liberty.” However, defending a homeland that is undergoing an invasion is just. For a war to be just, the conflict must have a just cause.
The third principle is the recognition that wars are always a last resort. It is only just to wage a military conflict if the prior criterion was met and all other means of attaining peace were already exhausted. Life is a treasured thing. The fact that governments across the world gleefully engage in war, so long as it does not harm them, is beyond grotesque. If civilization is going to advance in a safer and more human direction, wars must be only pursued as the last resort to solving a conflict; the ramifications of battle are too severe for this unjust practice to continue.
The fourth principle regards proportionality. In the ancient world, it was deemed as unjust for a charioteer to target infantrymen. Instead, the charioteer was called to fight charioteers. This principle was called the principle of proportionality.
The fifth principle is that the military conflict must have a probability of success. Without a probability of success, policymakers are throwing away the lives of their soldiers. Life is sacred. If one side cannot win—a victory is impossible—then waging such a conflict is unjust. The odds do not have to be in their favor. However, for the war to be just, there must be some probability of success.
Finally, one of the most important principles is that civilians cannot be targeted. Under this principle, the United States targeting Hiroshima and Nagasaki during World War Two was unjust because Hiroshima was largely populated by civilians and Nagasaki had no military bases. Civilians cannot be targeted in a just war.
In conclusion, there are six modern principles for a just war. Some of the principles deal with the just declaration of a conflict and others deal with how the conflict can be carried out justly. To reiterate all the principles, a war must be declared by the proper authority, have a just cause with a rightful intention, be a last resort, have a probability of success, exercise proportionality during the conflict, and not target civilians.
Asher Sisneros 