Opening Attack of Iraq War: On March 20, 2003 at approximately 02:30 UTC or about 90 minutes after the lapse of the 48-hour deadline, at 05:33 local time, explosions were heard in Baghdad. Special operations commandos from the CIA's Special Activities Division from the Northern Iraq Liaison Element infiltrated throughout Iraq and called in the early air strikes. At 03:15 UTC, or 10:15 p.m. EST, George W. Bush announced that he had ordered an "attack of opportunity" against targets in Iraq. When this word was given, the troops on standby crossed the border into Iraq.

Before the invasion, many observers had expected a lengthy campaign of aerial bombing before any ground action, taking as examples the 1991 Persian Gulf War or the 2001 invasion of Afghanistan. In practice, U.S. plans envisioned simultaneous air and ground assaults to decapitate the Iraqi forces quickly (Shock and Awe), attempting to bypass Iraqi military units and cities in most cases. The assumption was that superior mobility and coordination of Coalition forces would allow them to attack the heart of the Iraqi command structure and destroy it in a short time, and that this would minimize civilian deaths and damage to infrastructure. It was expected that the elimination of the leadership would lead to the collapse of the Iraqi Forces and the government, and that much of the population would support the invaders once the government had been weakened. Occupation of cities and attacks on peripheral military units were viewed as undesirable distractions.

Following Turkey's decision to deny any official use of its territory, the Coalition was forced to modify the planned simultaneous attack from north and south. Special Operations forces from the CIA and US Army managed to build and lead the Kurdish Peshmerga into an effective force and assault for the North. The primary bases for the invasion were in Kuwait and other Persian Gulf nations. One result of this was that one of the divisions intended for the invasion was forced to relocate and was unable to take part in the invasion until well into the war. Many observers felt that the Coalition devoted sufficient numbers of troops to the invasion, but too many were withdrawn after it ended, and that the failure to occupy cities put them at a major disadvantage in achieving security and order throughout the country when local support failed to meet expectations.

The invasion was swift, leading to the collapse of the Iraqi government and the military of Iraq in about three weeks. The oil infrastructure of Iraq was rapidly seized and secured with limited damage in that time. Securing the oil infrastructure was considered of great importance. In the Persian Gulf War, while retreating from Kuwait, the Iraqi army had set many oil wells on fire, in an attempt to disguise troop movements and to distract Coalition forces. Before the 2003 invasion, Iraqi forces had mined some 400 oil wells around Basra and the Al-Faw peninsula with explosives. Coalition troops launched an air and amphibious assault on the Al-Faw peninsula during the closing hours of March 20 to secure the oil fields there; the amphibious assault was supported by warships of the Royal Navy, Polish Navy, and Royal Australian Navy.

The United States Marine Corps' 15th Marine Expeditionary Unit, attached to the British 3 Commando Brigade and the Polish Special Forces unit GROM attacked the port of Umm Qasr. There they met with heavy resistance by Iraqi troops. A total of 14 Coalition troops and 30-40 Iraqi troops were killed, and 450 Iraqis taken prisoner. The British Army's 16 Air Assault Brigade also secured the oil fields in southern Iraq in places like Rumaila while the Polish commandos captured offshore oil platforms near the port, preventing their destruction. Despite the rapid advance of the invasion forces, some 44 oil wells were destroyed and set ablaze by Iraqi explosives or by incidental fire. However, the wells were quickly capped and the fires put out, preventing the ecological damage and loss of oil production capacity that had occurred at the end of the Persian Gulf War.

In keeping with the rapid advance plan, the U.S. 3rd Infantry Division moved westward and then northward through the western desert toward Baghdad, while the 1st Marine Expeditionary Force moved along Highway 1 through the center of the country, and 1 (UK) Armoured Division moved northward through the eastern marshland.

During the first week of the war, Iraqi forces fired a Scud missile at the American Battlefield Update Assessment center in Camp Doha, Kuwait. The missile was intercepted and shot down by a Patriot missile seconds before hitting the complex. Subsequently, two A-10 Warthogs bombed the missile launcher.

2003 Iraq War: The early morning of March 19, 2003, U.S. forces abandoned the plan for initial, non-nuclear decapitation strikes against fifty-five top Iraqi officials, in light of reports that Saddam Hussein was visiting his daughters and sons, Uday and Qusay at Dora Farms, within the al-Dora farming community on the outskirts of Baghdad. At approximately 05:30 UTC two F-117 Nighthawks from the 8th Expeditionary Fighter Squadron dropped four enhanced, satellite-guided 2,000-pound Bunker Busters GBU-27 on the compound. Complementing the aerial bombardment were nearly 40 Tomahawk cruise missiles fired from at least four ships, including the Arleigh Burke class destroyer, the USS Donald Cook, and two submarines in the Red Sea and Persian Gulf.

One missed the compound entirely and the other three missed their target landing on the other side of the wall of the palace compound. Saddam Hussein was not present nor were any members of the Iraqi leadership or Hussein family. The attack killed one civilian and injured fourteen others, including nine women and one child. Later investigation revealed that Saddam Hussein had not visited the farm since 1995.

Iraq War 2003: Since the 1991 Persian Gulf War, the U.S. and UK had been engaged in low-level attacks on Iraqi air defenses which targeted them while enforcing Iraqi no-fly zones. These zones, and the attacks to enforce them, were described as illegal by the former UN Secretary General, Boutros Boutros-Ghali and the then French foreign minister, Hubert Vedrine. Other countries, notably Russia and China, also condemned the zones as a violation of Iraqi sovereignty. In mid-2002, the U.S. began more carefully selecting targets in the southern part of the country to disrupt the military command structure in Iraq. A change in enforcement tactics was acknowledged at the time, but it was not made public that this was part of a plan known as Operation Southern Focus.

The amount of ordnance dropped on Iraqi positions by Coalition aircraft in 2001 and 2002 was less than in 1999 and 2000 which was during the Clinton administration. This information has been used to attempt to refute the theory that the Bush administration had already decided to go to war against Iraq before coming to office and that the bombing during 2001 and 2002 was laying the groundwork for the eventual invasion in 2003. However, information obtained by the UK Liberal Democrats showed that the UK dropped twice as many bombs on Iraq in the second half of 2002 as they did during the whole of 2001. The tonnage of UK bombs dropped increased from 0 in March 2002 and 0.3 in April 2002 to between 7 and 14 tons per month in May–August, reaching a pre-war peak of 54.6 tons in September – before Congress' October 11 authorization of the invasion.

The September 5 attacks included a 100+ aircraft attack on the main air defense site in western Iraq. According to an editorial in New Statesman this was "Located at the furthest extreme of the southern no-fly zone, far away from the areas that needed to be patrolled to prevent attacks on the Shias, it was destroyed not because it was a threat to the patrols, but to allow allied special forces operating from Jordan to enter Iraq undetected."

Tommy Franks, who commanded the invasion of Iraq, has since admitted that the bombing was designed to “degrade” Iraqi air defences in the same way as the air attacks that began the 1991 Gulf War. These "spikes of activity" were, in the words of then British Defence Secretary, Geoff Hoon, designed to 'put pressure on the Iraqi regime' or, as The Times reported, to "provoke Saddam Hussein into giving the allies an excuse for war". In this respect, as provocations designed to start a war, leaked British Foreign Office legal advice concluded that such attacks were illegal under international law.

Another attempt at provoking the war was mentioned in a leaked memo from a meeting between George W. Bush and Tony Blair on January 31, 2003 at which Bush allegedly told Blair that "The US was thinking of flying U2 reconnaissance aircraft with fighter cover over Iraq, painted in UN colours. If Saddam fired on them, he would be in breach." The Nuremberg Trials concluded that premeditated attacks on sovereign countries is aggression, the ultimate war crime.

United States military operations were conducted under the codename Operation Iraqi Liberation (OIL). The codename was later changed to Operation Iraqi Freedom, due to the unfortunate acronym. The United Kingdom military operation was named Operation Telic.

Multilateral support

In November 2002, President George W. Bush, visiting Europe for a NATO summit, declared that, "should Iraqi President Saddam Hussein choose not to disarm, the United States will lead a coalition of the willing to disarm him."

Thereafter, the Bush administration briefly used the term Coalition of the Willing to refer to the countries who supported, militarily or verbally, the military action in Iraq and subsequent military presence in post-invasion Iraq since 2003. The original list prepared in March 2003 included 49 members. Of those 49, only six besides the U.S. contributed troops to the invasion force (the United Kingdom, Spain, Australia, Poland, Portugal, and Denmark), 33 provided some number of troops to support the occupation after the invasion was complete. Six members have no military.

Invasion force

Approximately 248,000 soldiers from the United States, 45,000 British soldiers, 2,000 Australian soldiers and 194 Polish soldiers from Special Forces unit GROM were sent to Kuwait for the invasion. The invasion force was also supported by Iraqi Kurdish militia troops, estimated to number upwards of 70,000. In the latter stages of the invasion 620 troops of the Iraqi National Congress opposition group were deployed to southern Iraq.

A U.S. Central Command, Combined Forces Air Component Commander report, indicated that as of April 30, 2003, there were a total of 466,985 U.S. personnel deployed for Operation Iraqi Freedom. This included USAF, 54,955; USAF Reserve, 2,084; Air National Guard, 7,207; USMC, 74,405; USMC Reserve, 9,501; USN, 61,296 (681 are members of the U.S. Coast Guard); USN Reserve, 2,056; and US Army, 233,342; US Army Reserve, 10,683; and Army National Guard, 8,866.

Plans for opening a second front in the north were severely hampered when Turkey refused the use of its territory for such purposes. In response to Turkey's decision, the United States dropped several thousand paratroopers from the 173rd Airborne Brigade into northern Iraq, a number significantly less than the 15,000 strong 4th Mechanized Infantry Division that the U.S. originally planned to use for opening the northern front.

Operation Iraqi Freedom Preparation

CIA Special Activities Division (SAD) Paramilitary teams entered Iraq in July 2002 before the 2003 invasion. Once on the ground they prepared for the subsequent arrival of US military forces. SAD teams then combined with US Army Special Forces to organize the Kurdish Peshmerga. This joint team combined to defeat Ansar al-Islam, an ally of Al Qaida, in a battle in the northeast corner of Iraq. The US side was carried out by Paramilitary Officers from SAD and the Army's 10th Special Forces Group.

SAD teams also conducted high risk special reconnaissance missions behind Iraqi lines to identify senior leadership targets. These missions led to the initial strikes against Saddam Hussein and his key generals. Although the initial strike against Hussein was unsuccessful in killing the dictator, it was successful in effectively ending his ability to command and control his forces. Other strikes against key generals were successful and significantly degraded the command's ability to react to and maneuver against the US-led invasion force coming from the south.

SAD operations officers were also successful in convincing key Iraqi Army officers to surrender their units once the fighting started and/or not to oppose the invasion force. NATO member Turkey refused to allow its territory to be used for the invasion. As a result, the SAD/SOG and US Army Special Forces joint teams and the Kurdish Peshmerga were the entire northern force against government forces during the invasion. Their efforts kept the 5th Corps of the Iraqi army in place to defend against the Kurds rather than their moving to contest the coalition force.

According to General Tommy Franks, April Fool, an American officer working undercover as a diplomat, was approached by an Iraqi intelligence agent. April Fool then sold to the Iraqi false "top secret" invasion plans provided by Franks' team. This decoy deception successfully misled the Iraqi military into deploying major forces in Northern and Western Iraq in anticipation of attacks by way of Turkey or Jordan, which never took place. This greatly reduced the defensive capacity in the rest of Iraq and significantly facilitated the actual attacks via Kuwait and the Persian Gulf in the southeast.

Defending force

The number of personnel in the Iraqi military prior to the war was uncertain, but it was believed to have been poorly equipped. The International Institute for Strategic Studies estimated the Iraqi armed forces to number 538,000 (Iraqi Army 375,000, Iraqi Navy 2,000, Iraqi Air Force 20,000 and air defense 17,000), the paramilitary Fedayeen Saddam 44,000, Republican Guard 80,000 and reserves 650,000.

Another estimate numbers the army and Republican Guard at between 280,000 to 350,000 and 50,000 to 80,000, respectively, and the paramilitary between 20,000 and 40,000. There were an estimated thirteen infantry divisions, ten mechanized and armored divisions, as well as some special forces units. The Iraqi Air Force and Iraqi Navy played a negligible role in the conflict.

During the invasion, Iraqi forces, along with foreign volunteers from Syria, traveled to Iraq and took part in the fighting, usually under the command of the Saddam Fedayeen. It is not known for certain how many foreign fighters fought in Iraq in 2003, however, intelligence officers of the U.S. First Marine Division estimated that 50% of all Iraqi combatants in central Iraq were foreigners.

In addition, the terrorist group Ansar al-Islam controlled a small section of northern Iraq in an area outside of Saddam Hussein's control. Ansar al-Islam had been fighting against Kurdish forces since 2001. At the time of the invasion they fielded approximately 600 to 800 fighters. Ansar al-Islam was led by the Jordanian-born militant Abu Musab al-Zarqawi, who would later become an important leader in the Iraqi insurgency. Ansar al-Islam was driven out of Iraq in late March by a joint American-Kurdish force during Operation Viking Hammer.