There is a pretty wide gap between the actual bad guys who must be killed (Al Qaeda, other transnational terrorist groups, and the hard core of the insurgencies in many countries..the people who go around blowing up schools, chopping off hands of those who vote, etc.), and the majority of the enemy (who are purely mercenary foot soldiers, or common/pretty criminals, or some kind of tribal/ethnic group).

The ideal outcome is to separate the really bad guys and let tier-1 US units go after them (kill or capture; with kill being the most common outcome), while using politics and economics to reduce the number of the second category, convert them into either peaceful civilians or members of the security establishment in the country, etc.

Saddam, Uday, Qusay, and the other leaders: kill or capture Top-level baathists: prosecute using local courts Iraqi soldiers, local tribal militias, etc.: Bring them into the IP/IA/etc.

That's been the (successful) strategy since ~2006.

(I was actually AGAINST the Iraq war, because it was a distraction from going after Al Qaeda globally)