I seem to recall that in about 2002, a few vocal opponents of going into Iraq argued that the actual strategic problem for the US in the Persian Gulf area was Iran, and that taking down Iraq would only be doing Iran a favor.
Focusing on higher priority problems in the region was the better idea.
Hmm.
It looks like General Zinni was right. And now that I think of it,
I think he's right again (along with James Stavridis)