Defense of Others

The Sawicky doctrine of war-fighting:

. It should not be enough for some other nation to be an enemy, for it to have nuclear weapons, for it to be a tyranny, for there to be idle U.S. troops not engaged in some other war, for it to abuse its subjects or its neighbors, for it to be universally despised, for the U.N. to vote for its demise. My three exceptions would be 1) self-defense (in the face of an imminent, manifest, tangible threat, or act of aggression), naturally; 2) the threat of genocide, or 3) the near-guarantee of very great benefits at very low cost.

Here’s a question about this. If aggressive war is wrong (which clearly seems to be an underlying theme here), and wars of self-defense are justified, why isn’t it appropriate for a rich and powerful country like the United States to go to war in order to help defend a smaller, less-powerful country against acts of aggression committed by a third country? I’m not saying it’s always a good idea for the US to come to the defense of others, but the Sawicky Doctrine seems to hold that it’s always wrong to do this. Why would you think that?

UPDATE: In comments Max substantially concedes the point, “As long as that is what occurring, I don’t have a problem with that.” Obviously, the concept of defending others is open to abuse, particularly on the level of rhetoric. Then again, the concept of self-defense is likewise oft-abused in that virtually every war is soaked in the rhetoric of self-defense, often on absurdly far-fetched theories, but we still don’t abandon the concept. I should say that Max’s (2) strikes me as too lax in some ways and too strict in others.