This is the Spanish Civil War of our time. Much like Spain in the 1930s, there is no particular reason why the battlefield was selected. Both sides more or less converged on a location which became important simply because the enemy went there.

There are two basic objectives to define victory
1) Establish a stable allied government with security forces to enforce its will over the country
2) Prevent Insurgents from establishing their government and security forces over the country

The United States established an allied client states with security forces and the Insurgents failed. That’s it. Problems that go beyond these aims are not our concern as they are local issues. Under these objectives, the United States won. At this point in time, we are seeking to increase our margin of victory by making the allied state stronger and the remnant insurgents weaker.

It is irrelevant if there are some surviving insurgents in isolated regions. If they are unable to establish their own ruling government, they have been functionally defeated. We judge success by incremental gains and losses, not absolute categories.

Multiple wars have been fought in Iraq over the past 4 years. 
I will break the entire “war” into its component phases.
1) Overthrow of Ba’athist Regime (March-April 2003)
2) Defeat of Ba’athist Insurgency (April-December 2003)
3) Defeat of Sunni Populist Insurgency (April-December 2004)
4) Defeat of Shia Jaish al Mahdi Insurgency (April-May 2004)
5) Sucessful Sunni Al-Qaeda-led Network Insurgency (2005-2006)
6) Defeat of Al-Qaeda-led Insurgency (2007)

I will review each stage in detail.

The American Grand Strategy in Iraq is designed to counter the strategy of Zawahiri.

Zawahiri aims to launch terrorist attacks against the “Far Enemy” (US, Europe, India, etc) to rally support for the Islamist political movement. Once Islamists gain more popular support, they will overthrow the “Near Enemies” (Muslim governments)

Zawahiri realized the errors of the first Islamist military campaigns between the 1970s-90s. Islamists directly attacked the “Near Enemy” and intended to finish off the Far enemies later. Islamists attacked other Muslims and lost popular support.

The US intends to force the Islamists back into a civil war with the “Near Enemy” and in turn destroy popular back in Islamist countries. The US establishes allied Muslim states in Afghanistan and Iraq, forcing the Islamists to attack these Muslim states.

Grand Strategy
-Destroy Ba’athist sponsors of non-state warfare in the Middle East.
-Create ideological counter to radical Sunni and Shia Islamists.
-Change Balance of Power between Shia & Sunnis in the Middle East.
-Blur the Islamist distinction between “Near” Enemies and “Far” Enemies.
-Destroy ideological center of gravity for Arab Nationalism and Islamism

-Create a Client State in Iraq.
-Push for Democratic Governance in Iraq and challenge legitimacy of neighboring regimes.
-Create an Arab Shia dominated state for the first time in modern history.
-Raise Iraqi Security Force to handle internal security
-Muslim religious scholars weaken the religious basis of Revolutionary Islamism.

-Anglo-Saxon and Kurdish Military and Political Forces
-Native Iraqs and Kurds who resist Revolutionary Islamists.
-Orthodox Religious Scholars
-Al-Sistani and Shia mullahs of Najaf support orthodox Quietism and oppose radical Shia Revolutionary theology of Khomeini.
-Sunni ulema oppose terrorism against Muslims.

The War in Afghanistan temporarily removed the Islamists material center of gravity. The only way to achieve true victory is to destroy the ideological center of gravity in the Arab world. To do so, the US needs to challenge Arab Nationalism and Revolutionary Islamism. Most war objectives are somewhat irrelevant as they changed since the war began (it’s a wicked problem). The war was never entirely about the Ba’ath regime and certainly has nothing to do with it today.

The removal of the fascist Ba’ath Regime strikes a major blow against the remnants of Arab Nationalism and Pan-Arabism. It removed one of the three major state sponsors of non-state warfare in the region. Non-state warfare is the norm for the Middle East and Iraq funded or provided safe harbor for dozens of organizations to attack its neighbors – including Iran, Turkey, Kuwait, Israel and the US.

By these standards, the war is a minor victory so far because it discredited Arab Nationalism and Sunni Revolutionary Islamism. It may become a major victory if al-Sistani discredits Shia Revolutionary Islamism and if democracy takes hold as an alternative.

The war in Iraq became the central front in part to ease pressure elsewhere in the world. The war in Afghanistan would have been a failure had it not been for Iraq. Afghanistan is landlocked and located between two hostile states (Pakistan and Iran) with a large hostile Sunni population more accepting of Islamism. If Islamist forces converged and counterattacked in Afghanistan, the US would surely lose. However, Sunni Islamists converged on Shia-dominated Iraq instead, which is on more favorable ground to the US.

The War restructures the regional security situation. US troops no longer need to occupy Saudi Arabia, allowing greater diplomatic pressure against the Saudi regime. It spurred a nascent Lebanese independence movement to free itself of Syrian rule. US forces completely encircled Iran and forced Iran to make power-plays earlier than it wanted. Iranian aggression (Israel-Hezbollah War of 2006) and nuclear development has caused Sunni Arab states to rally together in opposition of an Iran-Syria regional alliance.