These Media Posts will serve as notification to the United States Congress that should Iran strike any U.S. person or target, the United States will quickly & fully strike back, & perhaps in a disproportionate manner. Such legal notice is not required, but is given nevertheless!— Donald J. Trump (@realDonaldTrump) January 5, 2020
Thomas Aquinas first considered the principle of proportional response when he described the doctrine of double effect in Summa Theologica. Aquinas explained that a single action can have have two effects: such as saving one’s life and taking another. If the good intention (read: saving one’s life) is the one aimed at, then self-defense can be justified. Including this principle of good intention, the doctrine of double effect includes four requirements, listed below from Joseph Managan1.
A person may licitly perform an action that he foresees will produce a good effect and a bad effect provided that four conditions are verified at one and the same time:
- that the action in itself from its very object be good or at least indifferent;
- that the good effect and not the evil effect be intended;
- that the good effect be not produced by means of the evil effect;
- that there be a proportionately grave reason for permitting the evil effect
Michael Walzer2 argues (and I agree with him) that a person committing an act also must incurr a reasonable amount of risk in order to minimize the amount of harm caused.
Proportionality is fundamental to the exercise of modern warfare. The things we do in war should be for a specific military advantage that works towards a well-defined political goal. A disproportionate response to any particular provocation by an enemy, such as Iran, is by definition conducting military operations without regard to the military advantage sought. In other words: pointless. And illegal.