[Disclaimer: I claim no competence in the Catholic just war tradition beyond catechism basics]
The Church has long taught a just war tradition (cf. CCC 2307-2317), specifying the conditions under which war might be justly declared and waged. As Bl. John Paul II said in an address to soldiers,
Peace, as taught by Sacred Scripture and the experience of men itself, is more than just the absence of war. And the Christian is aware that on earth a human society that is completely and always peaceful is unfortunately an utopia and that the ideologies which present it as easily attainable only nourish vain hopes. The cause of peace will not go forward by denying the possibility and the obligation to defend it.
And addressing the nobility of the call to serve in the armed forces, the Pope affirmed,
…a tribute to your many friends who have paid with their lives for fidelity to their mission. Forgetting themselves and despising danger, they rendered the community a priceless service. Today, during the Eucharistic celebration, we entrust them to the Lord with gratitude and admiration. But where did they find the strength necessary to do their duty to the full, other than in total adherence to the professed ideals? Many of them believed in Christ, and his words illumined their existence and gave an exemplary value to their sacrifice.
That said, the Church has also proclaimed a concomitant “pacifist” tradition of non-violent resistance to evil. As the Catechism, paragraph 2306 says it,
Those who renounce violence and bloodshed and, in order to safeguard human rights, make use of those means of defense available to the weakest, bear witness to evangelical charity, provided they do so without harming the rights and obligations of other men and societies. They bear legitimate witness to the gravity of the physical and moral risks of recourse to violence, with all its destruction and death.
Both traditions need to be attended to, though it’s not always possible to reconcile them in any particular circumstance. Recent popes have clearly favored a robust “avoidance of war through peaceful means” approach, while Pope Francis has come much nearer, in his rhetoric, to the pacifist tradition. Francis clearly sees war as a “defeat of humanity,” even when the cause is just — as Monday’s papal tweet revealed: Numquam plus bellum! Numquam plus bellum! “Never again war!”
Bl. John Paul II reflected the tone of this pacific tradition’s voice when he said in Crossing the Threshold of Hope,
Humanity should question itself, once more, about the absurd and always unfair phenomenon of war, on whose stage of death and pain only remains standing the negotiating table that could and should have prevented it.
Apostles of the Lamb
Even as one engages in the irreducible complexities of statecraft by rendering prudential judgments about whether or not it is “right and just” to employ deadly force in service to strategic ends that serve a just peace, the Church, distinct from the State, cannot lose sight of her absolutely unique mission in the world. Vatican II said it this way,
Christ gave His Church no proper mission in the political, economic or social order. The purpose He set before her is a religious one. But out of this religious mission itself came a function, a light, and an energy which can serve to structure and consolidate the human community according to the divine law…Moreover, since in virtue of her mission and nature she is bound to no particular form of human culture, nor to any political, economic or social system, the Church by her very universality can be a very close bond between diverse human communities and nations, provided these trust her and truly acknowledge her right to true freedom in fulfilling her mission. For this reason, the Church admonishes her own sons, but also humanity as a whole, to overcome all strife between nations and race in this family spirit of God’s children, an in the same way, to give internal strength to human associations which are just. (par. 42)
This distinctive mission is one that Mennonite-tradition pacifist Stanley Hauerwas reflects on here with his usual incisiveness:
That is why Christian realism requires the disavowal of war. Christians do not disavow war because it is often so horrible, but because war, in spite of its horror – or perhaps because it is so horrible – can be so morally compelling. That is why the church does not have an alternative to war. The church is the alternative to war. When Christians lose that reality – that is, the reality of the church as an alternative to the world’s reality – we abandon the world to the unreality of war.
As the Catechism reminds us that “[a]ll citizens and all governments are obliged to work for the avoidance of war,” so we as Catholics must ora et labora, “pray” and “work” for the success of war’s avoidance and the equal success, in our present circumstance, of a peaceful and just resolution to the evils of violence and injustice in Syria and elsewhere.
I am convinced we should pray especially to the “white robed army” of martyrs from the Middle East, and from all places past and present, whose heroic witness of self-sacrificing love in the face of hatred and violence placed them with Jesus on the Altar of the Cross from whence flows the omnipotent reconciling peace of the eternally Pacific Trinity. Martyrs remind us that those who sow in peace must also freely face the brutality of humanity without illusion, and must do so with a heart steeled by God’s fearsome mercy made known to us in the “Lamb slain from the foundation of the world.” (Rev. 13:8)
Genesis says that we began in a swamp teeming with life, but that something went vastly wrong one evening at dinner. Apocalypse says that the difficult was finally resolved into something called the Banquet of the Lamb. Hebrews tells us how the resolution was accomplished, not in an orchard set in pleasant countryside but in a butcher shop located in the city’s center. The World’s story from beginning to end pivots upon this resolution, a resolution the faint of heart, the fastidious, and the squeamish find hard to bear. Suburbia prefers its meat wrapped in plastic, all signs of violence removed so as to reduce the necessity of entering into the dark and murderous transaction with reality which one creature giving up its life for another entails. — Fr. Aidan Kavanagh, On Liturgical Theology