RR Reno ponders Just War theory here in relation to the ongoing operation Epic Fury in Iran. Just War theory has a long history in Christianity. You can read the history of Just War theory here. While Augustine commented on it, Aquinas provided the most extensive thinking on the subject. In his Summa Theologicae, Aquinas presents the general outline of what became traditional just war theory. He discusses not only the justification of war but also the kinds of activity that are permissible (for a Christian) in war. The principles of Just War theory are here.

Reno soundly concludes,

The fog of war is proverbial. In the Middle East, one can say the same of peace, which is often war by other means. The circumstances of American involvement in that region are morally complex. For this reason, it is unwise to issue confident moral judgments about Operation Epic Fury.