a complete surrender would be even better
think of al-Sadr (not that we can trust his mob yet, of course) - or for that matter, Gaddafi. Having the world watch these guys competely fold and buckle under to civilized authority, is a greater and more effective victory than just wiping them out. By all evidence, the US and the Coalition would prefer that outcome too. Wiping them out is hopefully regarded as a last necessary recourse.