It's complicated, because it started out as "smash the state and let democracy reassert itself". Everyone involved in the room had such a broken mental model of what the Iraqi population was like. American politicians have been getting drunk off the rhetoric of democracy for some time, and we typically forget that most governments are precariously balanced between multiple competing socioeconomic elements with eternal and unending grudges between one another. In the case of Iraq, what started as "invade and impose democracy" quickly progressed into policing sectarian violence as America inherited Saddam's problems.

Iraq began as an invasion in March 2003. The invasion was exceedingly well planned and executed with minimal cost in a very short time frame, but the planning did not account for the resulting occupation that followed.

Key figures in Iraq, such as Ali Al Sistani, pressed US civilian authorities to stand up an interim government until a permanent government could be drafted. The interim government stood up in May 2004. But by that time Iraq had become a political vacuum with disastrous results. Various external political factions from terrorist groups and nation states were massively importing arms and radicalized youth to instigate internal tribal warfare and acts of terrorism.

Shortly after the interim government stood up GEN Casey took over command of coalition forces in Iraq and promoted a hand's off policy and letting the Iraqis clean up the mess, which further compounded the internal problems when Iraq really needed a strong occupation force to stabilize conditions until conditions allowed the capabilities for self governance. GEN Casey was replaced two years later in 2006.

In mid-2006 it really looked like Iraq was on the verge of civil war and the US completely reversed policy by late 2006 announcing a troop surge in 2007. The successful command policies of COL HR McMaster were given some credit for exemplifying a successful approach. GEN Petraeus took command of coalition forces in Iraq and advocated a policy of counter-insurgency (COIN) that made significant advances at reducing internal violence and building trust in internal institutions. Over the next two years the surge declined to prior troop levels with forces more engaged in peace keeping and stability missions.

In 2009 coalition forces were drastically reduced in what was called a withdrawal. By that time Iraq was no longer on the verge of civil war. Conditions were improving and permanent government institutions were coming online. Unfortunately, the withdrawal was too early. Newly established Iraqi military forces were still conducting peace keeping and stability missions and had not matured enough yet to focus on national defense. This became apparent with the ISIS invasion of Mosul.