Here is a commentary provided to Catholic News Service written by Stephen M. Colecchi, who retired as director of the Office of International Justice and Peace of the U.S. Conference of Catholic Bishops in 2018. He currently serves as an independent consultant on Catholic social teaching and international issues of concern to the church.

Russia's invasion of Ukraine raises fundamental moral questions that Catholic teaching can help us to explore.

I accompanied bishops on a solidarity visit to Ukraine in 2015. In Kyiv, their independence monument represented for me the soaring spirit of the Ukrainian people. We visited memorials to those who lost their lives to protect Ukrainian democracy.

Acknowledging that too often "just war" norms have been used to justify war, I believe Russia is waging an "unjust war" and Ukraine is waging a "just defense." The moral distinction is important.

Significantly, the Catechism of the Catholic Church discusses "just war" in a section entitled "avoiding war."

"All citizens and all governments are obliged to work for the avoidance of war" (#2308). The catechism lists "strict conditions for legitimate defense by military force" as follows:

– the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;

– all other means of putting an end to it must have been shown to be impractical or ineffective;

– there must be serious prospects of success;

– the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition (#2309).

The catechism goes on to declare that non-combatants "must be respected and treated humanely" and that actions "deliberately contrary to the law of nations ... are crimes" (#2313).

Russia failed in its obligation to "avoid war." Russia used military exercises as a fig leaf for its war preparations. The consequences of its invasion for Ukraine and the world order are "lasting, grave, and certain." Russia's actions have produced grave evils. Innocent civilians have been targeted. Such actions are crimes.

But what of Ukraine's armed defense and of the West's arming of Ukraine? I would argue that it is morally licit for Ukraine to defend its citizens and that it is licit for the West to assist them in this regard. As the defense of Kyiv demonstrates, there are "serious prospects of success." To date, the actions of Ukraine's defenders have not produced "evils and disorders graver that the evil to be eliminated." On the contrary, numerous reports indicate that Russia's actions have violated international norms and may constitute war crimes.

Beyond assisting Ukraine with its defense, it is morally obligatory for the West to help protect non-combatants who have fled the war zone as displaced persons and refugees to other countries. Civilians, especially children, have suffered disproportionately and indiscriminately. They require our protection and assistance.

At the same time, Ukraine must explore every reasonable effort to negotiate an end to the war. This obligation weighs even more heavily on Russia as the aggressor. The legitimacy of armed defense does not dispense with the obligation to "avoid war."

In addition, Ukraine and the West must be careful not to escalate the conflict. As the catechism admonishes: "The Church and human reason both assert the permanent validity of the moral law during armed conflict. 'The mere fact that war has regrettably broken out does not mean that everything becomes licit between the warring parties'" (#2312).

Avoiding indiscriminate bombings and the risk of nuclear escalation are paramount in this regard. The catechism reminds us that a "danger of modern warfare is that it provides the opportunity to those who possess modern scientific weapons – especially atomic, biological, or chemical weapons – to commit such crimes" (#2314).

Beyond the immediate conflict, the West and Russia need to work to avoid another Cold War, with an accompanying arms race. The catechism is clear in this regard. "The arms race does not ensure peace. Far from eliminating the causes of war, it risks aggravating them.

Spending enormous sums to produce ever new types of weapons impedes efforts to aid needy populations; it thwarts the development of peoples. Over-armament multiplies reasons for conflict and increases the danger of escalation" (#2315).

There is a moral risk in arming Ukraine. We must remember that war does not produce peace. Peace is built on the foundation of justice and human rights. The soaring spirits of Ukraine and humanity must reach for a just peace.