I think that NATO's intervention can be explained by looking at the stated
aims and comparing them to predicted outcomes.  Starting from the two
reasons Tresy Kilbourne cites: 1) stopping
the humanitarian catastrophe in the Balkans and 2) tell Milosevic that the
West means business.  As for 1), it is clear that the humanitarian
catastrophe was escalated, not prevented by NATO bombings.  Wesley Clark,
and others, predicted as much.  Indeed, pulling out OSCE monitors, refusing
to negotiate for armed peacekeepers (see the counteroffer from the Yugoslav
parliament in March), and bombing the country with impunity from the air,
had the predictable effect of escalating the war.  As for 2), I think that
this is actually a reasonable explanation, and one proffered quite often by
NATO and US planners as the humanitarian line became more difficult to hold:
NATO credibility was at stake.  Obviously, as Chomsky has said, we're not
talking about the credibility of Denmark here.  With Germany becoming active
in organizing the political space in the disintegrating Balkans, and the EU
and OSCE also threatening to push their way into the scene as arbiters and
agenda setters, the US had important interests at stake in ensuring that
NATO hold on to and enhance its central role in European military and
political planning.   Why?  Because NATO is a US-led organization, while the
others are not.  Re-asserting the value of military action over diplomacy is
also an important accomplishment, as well as striking a blow against the
norms of international law and UN oversight.  In each of these cases, the US
discourages the use of forums in which it is relatively weaker (diplomacy,
UN) in favor of forums in which it is relatively stronger (cruise missiles
and air strikes).  Perfectly understandable to me, at least.

I think each of these points need a bit more context and discussion, but
that's the best I can do on the spur of the moment in ~300 words.

Soren