He suffered mightily in Vietnam
It was due to HIS judgement that the USS Cole was in Yemen.
Now, taking those two things into consideration I think he might have a bit of an over reaction to the situation in Iraq.
I have never been impressed with the foreign policy expertise of the CINCs who have become proconsuls with grandiose ideas. What makes Zinni such an expert on the Middle East? Powell selected him to be the US Special Envoy. Unfortunately, the military has eclipsed the rest of the US foreign policy community in terms of influence. They have the resources, i.e., military equipment and training, to curry favor with other countries and to gain entree to their leaders.
I can recall being upbraided by Deputy Chairman of the Joint Chiefs about the State Department stopping the military exchange program with Indonesia because of East Timor. He couldn't understand why it would be politically inappropriate to continue to support the very people who were undermining our efforts to stop the violence in East Timor.
Clark is another example of someone with an inflated idea about his foreign policy expertise. It makes me laugh when he touts his "major" role in the Dayton accords and his relationship with Milosevic. Clark was a messenger boy for Holbrooke and Albright. His influence was virtually nil, which is why he tried to do his own thing and was fired.