The Middle East is filled with Islamic countries where a ruthless and brutal leadership is a necessary ingredient for stability. Promoting “democracy” in places like Iraq is like teaching molecular physics to preschoolers.
That is why you need a stable ground force that stays the course, and the children growing up see the difference in the previous governance and the benefits of the changes. We had to do that in Germany, Japan and to some degree, the Philippines to get more stable leadership into those countries.
There were huge problems in both Germany and the Philippines with U.S. troops and elements which still wanted to fight.
Only Japan was truly unconditional in its surrender.