In this essay, the author James Baresel condemns the "national interest" argument and argues that "just wars" are undertaken only on a moral basis. Since, following PJ Buchanan we've used the "national interest" argument, we'll present elements of Baresel's essay. You should read the whole thing.
...After over a century of foreign policies guided by false ideologies,
from the hostility to traditional monarchal and aristocratic government
euphemistically termed “making the world safe for democracy” to the
radical extremes of social liberalism, realists’ professions of
“traditionalist conservatism” increase the attractiveness of what is
actually a negation of traditionalist conservative political morality—a
school of thought which replaces false principles not with true ones but
with amoral materialistic pragmatism.
Agreeing with classical ethics and Christian theology, Edmund Burke
insisted that “the principles of true politics are those of morality
enlarged.” After all caveats are made, foreign policy must still be
grounded primarily on moral considerations—on determining how a nation
can realistically pursue goodness and justice—rather than material
national interests. If self-destruction in pursuit of chimeras will not
aid the cause of worldwide justice, some sacrifice of national interest
in that cause is usually legitimate and at times a moral obligation.
Just war principles are clear on this....
He cites a Jesuit on the topic:
....Fr. Joseph McKenna stressed that “assessment [of whether the good to be
achieved outweighs the harm] must be made in terms of moral rather than
material gains and losses”—so much so that “In extreme cases the moral
value of national martyrdom may compensate for the material destruction
of unsuccessful war.”...
We would suggest that Fr. McKenna's 'in extremis' suggestion would logically baptize suicide as a virtuous act. Now "suicide" may be the wrong term if "accepting martyrdom for the sake of justice" is the reality; look at St. Maximilian Kolbe as a modern example of that. But our objection to Fr. McKenna's position is this: one may choose martyrdom for oneself (given all the usual.) But one may NOT choose martyrdom for others.
This brings up the 'yellow-bellied Chamberlain' discussion. Some argue that in reality, England was in no military (nor financial) position to undertake war with Hitler at the time. Ad arguendam if that is true, would it be 'morally compelling' for Chamberlain to have launched a hot war at the time?
It is interesting that Baresel actually makes the case for Putin's SMO (!)
...Justifications for war in the Catholic Encyclopedia include
“the need of punishing the threatening or infringing power,” “oppression
of the innocent, whose unjust suffering is proportionate to the gravity
of war and whom it is impossible to rescue in any other way,” and
“request of another state in peril.”...
The population of eastern Ukraine is largely Russian, and the Ukrainian government put into place by the US has been terrorizing, bombing, and murdering those Russians since 2014. Putin's SMO was initiated to rescue those Russians from 'unjust suffering' (or so Putin says.)
So under Baresel's analysis, Putin's move is a morally-justified operation if we accept that Putin did not initially use overwhelming force to prod Zelenskiy (and the US) into halting their 'infringing power.' IOW, Putin holds the moral high ground here. Following that logic, any US (or NATO) involvement would then be immoral.
YMMV.
...While the Catholic Encyclopedia teaches that securing justice
for others through altruistic wars is just, and common sense tells us it
is noble, what is neither a necessary precondition nor a justification
for war is “national interest”—a material consideration rather than a
moral one. Even when fighting injustices detrimental to national
interests, it is the injustice alone which makes use of force
legitimate....
Well, then, is it morally correct for the US to take on Red China over the Uyghurs? Or to take on the Moslem Africans in defense of the Christians who are being slaughtered in the name of Allah?
One more thing: War can be conducted without arms and armies. There are various economic and political means by which a rogue state may be brought to heel without committing national suicide. Perhaps Mr. Baresel will essay on those possibilities in the future.