The First Phase lasted from March 20th to the end of April. There’s no definitive end date, but the fall of Baghdad on April 9th marked the end of the Ba’ath regime.

This is a brief review of the invasion
Iraq Defense Strategy
• Regular Army placed near Kuwait and Kurdistan borders (~350k troops)
• Fedayeen and Ba’ath Party militia hold towns and cities (~50k)
• Republican Guard holds Baghdad (~50k)

Flaws in Strategy
• Saddam stationed the Republican Guard in the rear and in the open. The US Air Force bombed the Republican Guard and US ground forces destroyed the remnants.
• Iraq did not destroy bridges or defend major choke points
• The Iraqi Army faced problems with corruption, poor maintenance, and “ghost soldiers” (inflated pay-rolls that exaggerated real unit strength)
• Much of the Army deserted or disbanded
• Fedayeen and Militia forces used weak hand-held weapons
• Militias were the principle resistance force despite having the weakest capability

In general, the strategy was inept and backwards. The Republican Guard should have engaged US forces first, with the Army in support. The Militias should have held rear ground areas or used guerrilla tactics to supplement professional troops. The Fedayeens and Militias could not put up serious resistance to stop or reverse the US invasion.

US Invasion Strategy
This is a good map detailing the unit positions and invasion routes.

Force Deployment: USA (120k) UK (45k) Kurdish Peshmerga militias (deployed 50k)

• USAF surgical strikes disrupt Iraqi communications and command.
• US Marines and Army advance up Euphrates and Tigris and take Bagdad
• The British Army takes Basra
• US 101st Airborne and Kurdish Peshmerga take Mosul, Kirkuk and Diyala
• Used Blitzkrieg tactics. US left small detachments to check Fedayeens in towns as US forces bypassed hostile regions and continued towards Baghdad

Flaws in Strategy
• Turkey denied passage to the 4th Mechanized Infantry. This weakened the Northern Invasion force.
• Ultra-rapid collapse of Iraqi state within 3 weeks
• Insufficient forces to hold major cities outside Kurdish-held regions
• Permitted widespread looting due to fears of inflicting civilian casualties
• Iraqi military units disbanded or deserted in mass. The US could not control or rebuild the Iraqi Army in 2003.
• Fedayeen and Ba’ath Militias scattered and began the insurgency
• Shia religious militias (Mahdi, Badr, etc) ruled much of Shia Iraq.

This is an undisputed US military victory. It eliminated the Ba’ath Regime and installed an occupational government. This is also a major win for Kurdish autonomy. The political situation with the Shia remained ambiguous.

State-Sponship of terrorist and insurgent organizations ended. The US cut off Iraqi funding for Islamist organizations like Islamic Jihad and Hamas. It cut off funding and support for other organizations like the PKK, Abu Nidal Organization, and a list of others. US forces surrounded and captured the MKO militant organization. The Kurds expelled the al-Qaeda associated movement Ansar al-Islam. The Iraqi Intelligence Agency – The Mukhabarat – was dismantled.

In the end, Sunnis (about 20% of the population) refused to admit defeat and loss of their empire. Sunnis traditionally ruled Iraq for centuries despite minority status. Sunni Tribes and former Ba’athists continued to fight using guerilla tactics.