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“War is Hell.” This quotation from Union General William Tecumseh Sherman is sometimes used to mistakenly imply that ethics does not apply to warfare. As harsh as Sherman was in deliberately and systematically destroying civilian property, crops, and livestock, even he drew a line at deliberately killing the noncombatants he made homeless.  

Over the centuries, the Church and international conventions have made tremendous efforts to lessen the horrors of war and enforce ethical rules in combat. The commonly used legal term, war crimes, shows that certain actions in time of war are punishable under national and international laws. The military in the US and elsewhere have codes of ethics and legal requirements for their members’ actions in war. A very dramatic example is the requirement that soldiers refuse “unlawful orders” that would have them commit a war crime.  

Please excuse my broad strokes as I summarize the more than millennial debate on the ethics of war and make a few points about the ongoing invasion of Ukraine. As a bioethicist my academic specialty is not the ethics of armed conflict, but I have had a lifelong interest in military history and the Catholic perspective on warfare.

There is a very long tradition of ethical debate on the nature of war, particularly what is or is not a “Just War.” No less of a figure than the Angelic Doctor, St. Thomas Aquinas, discussed it in his Summa Theologiae. His main points were that war is a public action of last resort that cannot be engaged in for sinful reasons. There must be rightful intentions and a just cause, as well as proportion between the good to be achieved and the evils of war. He also pointed out the moral responsibility of not intending intrinsically evil actions among those trying to fight a war in an ethical way.

The pacifist view that war can never be ethically justified has been a minority opinion among Christians, but certain denominations, like the Mennonites and Amish, hold this as a key religious belief. The Catholic Church increasingly views war as a moral catastrophe to be avoided at almost all costs. Nevertheless, the Catechism of the Catholic Church (n. 2309) points to conditions that apply to “legitimate defense by military force.” In the Catholic moral tradition it is much easier to mount an ethical defense of a defensive war than an offensive or preemptive one.

The current war in Ukraine is clearly an example of a grave ethical violation, the crime of aggressive war. Russia invaded its neighbor with a massive military force over disputes that might still have been resolved through diplomatic negotiations. Russia faced no existential threat from Ukraine that could make military attacks a proportionate response.

The main justification provided from the Russian side is that the Ukrainians are closely related to the Russians and Ukraine’s turn towards the West in recent years, and even discussion of membership in the NATO military alliance, was a betrayal of and threat to Russia. Anti-Russian feeling in Ukraine grew after the military seizure and annexation of the Crimea by Russia in 2014 as well as its protection of breakaway republics in eastern Ukraine. The last two actions came as a reaction to the toppling of a pro-Russian Ukrainian president.

One of the more complicated legacies of the Soviet Union is a significant population of people, largely in eastern Ukraine, who speak Russian rather than Ukrainian and feel culturally more tied to Moscow than to Kiev. The ease with which Vladimir Putin succeeded in taking Crimea and negating Ukrainian control of several eastern parts of the country seems to have led to his miscalculation that it would be simple to forcibly replace the current Ukrainian government. He thought that an overwhelming military strike aimed at large parts of the country, including the capital, would face only token resistance.  
The ongoing war has raised significant war crimes concerns. International law has created safeguards for civilians that were not in place when General Sherman’s army burned and destroyed a huge amount of property from Atlanta to the sea. The Geneva Convention stipulates that those engaged in armed conflict will at all times direct their operations only against military objectives and avoid targeting civilians and civilian objects.

There are multiple credible reports of Russian indiscriminate attacks on private buildings and people, including hospitals. These are being investigated. I have not seen any evidence the Ukrainian military has attacked Russian territory or Russian civilians, so the ethical picture shows a sharp contrast between Russian aggression and violations of the rights of non-combatants and Ukrainian actions limited to defense of their territorial integrity.

The big question for third parties in nations around the world is, what are we called to do? There is a moral imperative to give humanitarian assistance to war refugees—several million people and increasing. Providing aid to the side that in our judgment has a just cause and is fighting ethically is reasonable as well.

Prudential arguments about what actions on the part of the US or other countries might risk broadening the scope of the war should be ethically evaluated. Especially if one is not directly attacked, joining a conflict materially, or as a co-combatant, requires analysis to see if just war criteria are met. Historically, the decisions to join in wars have sometimes been for cynical or Machiavellian reasons and at other times were emotionally driven. We should avoid both traps. The humanitarian impulse to go to war—to end human rights abuses, remove a dictator, etc.—is particularly fraught with danger. One runs the terrible risk of the “cure” being worse than the original disease.

War is always a tragedy and a failure of the commandment to love our neighbor as ourselves. Both sides in an armed conflict can be in the wrong. In the best of circumstances, only one side can have a just cause, but frequently there are grievances on both sides that grow as the killing continues. The “logic of war” is a very dangerous dynamic that must be resisted. Nations can be sucked into conflicts and led to escalate the scale of killing and destruction as wars drag on. As we pray for peace, it is good to be keenly aware of the dangers and ethical challenges of war.