The Iranian intervention in Iraq has its roots in the 2003 invasion of Iraq by the United States and its allies, when the infrastructure of the Iraqi armed forces, as well as intelligence, were disbanded in a process called "de-Ba'athification" which allowed militias with close ties to Tehran to join the newly reconstituted army.
The intervention reached its peak following the advance of the Islamic State into northern Iraq in mid-2014. Iran began to provide military aid to counter the militant advance. Iran provided technical advisers to the Iraqi government and weapons to the Kurdish Peshmerga. Several sources, among them Reuters, believe that since mid-June 2014, Iranian combat troops are in Iraq, which Iran denies.
The Iraqi Shia militias Kata'ib Hezbollah ("Hezbollah Brigades") and Asa'ib Ahl al-Haq ("League of the Righteous"), funded and trained by Iran, fought alongside the Iraqi Army and Peshmerga in retaking territory from ISIL.
Background
US invasion of Iraq
After the 2003 invasion of Iraq by the United States and its allies, The Coalition Provisional Authority disbanded the Iraqi military, security, and intelligence infrastructure of President Saddam Hussein and began a process of "de-Ba'athification". This move became an object of controversy, cited by some critics as the biggest American mistake made in the immediate aftermath of the fall of Saddam Hussein and as one of the main causes of the rise of the Islamic State.
The Badr organisation, which fought alongside Iran in the Iran-Iraq war, was seen as a U.S. asset in the fight against Ba'athist partisans because of their opposition to Saddam Hussein. Shortly after the fall of Baghdad, Badr forces and other militias with close ties to Tehran reportedly joined the newly reconstituted army, police, and Interior Ministry in significant numbers. The Interior Ministry was controlled by SCIRI, and many Badr members became part of the Interior Ministry-run Wolf Brigade. The Iraqi Interior Minister, Bayan Jabr, was a former leader of the Badr Brigade militia.
The Islamic Supreme Council of Iraq and various other parties with military wings, all with close ties with Tehran, had pioneering role in forming the governments with close ties to Tehran.
According to the U.S. military and U.S. State Department, the Iraqi Shia militia Kata'ib Hezbollah ("Hezbollah Brigades"), which has existed since 2003, has received funding, training, logistics, guidance, and material support from the Iranian Islamic Revolutionary Guard Corps's Quds Force. Iran denies these claims.
Asa'ib Ahl al-Haq ("League of the Righteous"), another Iraqi Shia militia, formed in 2006, was assumed by Iraqi officials to have been receiving $2 million a month from Iran even before 2014, and assumed by The Guardian to be under the patronage of Qasem Soleimani.
Opposing the intervention
In 2019, protests broke out in Iraq demanding the end of corruption, nepotism, unemployment, and political sectarianism while also calling for an end to Iranian intervention in Iraqi affairs. The Abdul-Mehdi government, backed by Iranian-backed militias used live bullets, marksmen, hot water, hot pepper gas, and tear gas against protesters, leading to many deaths and injuries.
The protests resulted in the resignation of Prime Minister Abdul-Mahdi and his government, and the appointment of Mustafa Al-Kadhimi. A new election law was also passed by the Council of Representatives.
The 2021 parliamentary election resulted in Pro-Iran parties losing seats in the newly elected Iraqi parliament and in turn led to 2021 Baghdad clashes.
In November 2021, Al-Kadhimi survived an assassination attempt via an explosive drone, two drones were shot down by the army while the last one targeted his residence in the heavily fortified Green Zone district of Baghdad.
According to experts, the assassination attempt came as a response to pro-Iran parties losing seats in the 2021 Iraqi parliamentary election.
Intervention
Strategy and tactics
Tehran's strategic objectives in its intervention in Iraq include keeping the Shia-led government in power and stabilising its border.
Iran has attempted to limit its overt military involvement in Iraq as a strategy geared toward avoiding the polarisation of Iraq's Sunni minority, creating a popular backlash against Iran among Iraqis, or deepening sectarian tensions. The IRGC also attempted to create a more diversified model in Iraq, and began interacting more with Iraqi Turkmen and Feyli Kurds. Most Iranian aid has thus far come in the form of technical assistance, the commitment of special forces troops, and air support. Iranian Brigadier-General Massoud Jazayeri stated that Iran could best help Iraq by providing it with direction on its "successful experiments in popular all-around defence" that included "mobilising masses of all ethnic groups." Iran believes cooperation and unity among Iraq's fractious militias are essential in its battle against ISIL. Ali Khamenei, in remarks delivered on 15 September 2014, credited "the people of Iraq, the Iraqi Armed Forces, and the popular forces" for halting the ISIL advance of the previous summer.
The Washington Post reported that Iran has sent more than 1,000 military advisers to Iraq, and spent more than $1 billion on military aid.
Timeline
June 2014
In the week of 14 June, according to The Guardian, Iran's Quds Force commander Qasem Soleimani was in Baghdad to organise an Iraqi counterattack against ISIL. Press agency Reuters believes that since mid-June, Iran has had members of its Islamic Revolutionary Guard Corps (IRGC) fighting on the ground in Iraq against ISIL, though it does not give an estimate of their numbers.
According to Iranian social media, ISIL troops on 19 June attacked two Iranian border guards near Iran's border city of Qasr Shirin, but this has not been confirmed by authoritative sources.
American war correspondent David Axe, on his website 'War is Boring', asserted that on 21 June 2014, "it appears Iran joined the air war" of Iraq and Syria against ISIL.
By the end of June, according to American officials, Iran had established a control center at Al-Rasheed Air Base in Baghdad and was flying a small fleet of Ababil drones over Iraq, and an Iranian signals intelligence unit had been deployed at the airfield to intercept electronic communications between ISIL fighters and commanders.
July 2014
On 1 July, according to IISS, several Su-25 aircraft were sent by Iran to al-Rashid and, later, to the al-Muthanna air base. The aircraft were supported by bi-national Iranian/Iraqi ground crews who had been trained in Iran. (During the 1991 Gulf War, seven Su-25s had been flown by the Iraqi air force to Iran as a temporary safe haven, and Iran had kept them since; ironically, some of them may now have returned to Iraq.)
On 5 July, Quds Force pilot Shojaat Alamdari was killed in Samarra, probably working there as a forward air controller.
August 2014
Iraqi Kurdish President Barzani and Iranian foreign minister Zarif said, at the end of August 2014, that Iran had been the first country to provide weapons and ammunition (at an unspecified date) to the Iraqi Kurdish forces (Peshmerga). Zarif said that Iran cooperated militarily with the Iraqi central government and the Kurds, but that it had "no military presence in Iraq".
In contradiction to that Iranian denial, Business Insider, without naming its sources, contends that in early August, Iran's IRGC sent Quds Force personnel, attack aircraft, and drones to Iraq and that since early August Iran was operating its Su-25 aircraft (see July 2014) in combat against ISIL.
But in early August, Qasem Soleimani, chief of the Iranian Quds Force, was indeed in Erbil advising Kurdish forces, an Iranian official admitted in early October 2014.
On 21–22 August, according to Kurdish sources, hundreds of Iranian soldiers, allegedly from Iran's 81st Armored Division, helped Peshmerga to take back Jalawla in Diyala Governorate from ISIL. Iran subsequently denied any military presence in Iraq.
There were unconfirmed reports of clashes between ISIL forces and Islamic Revolutionary Guard Corps units near Urmia on 28 August.
Between 31 August and 1 September, the Iranian-backed Iraqi Shia militias Asa'ib Ahl al-Haq and Kata'ib Hezbollah (see section Background) joined an Iraqi army and Kurdish Peshmerga assault to break the ISIL siege of Amerli in Saladin Governorate. The attack was supported by the U.S. Air Force at the request of the Iraqi army, according to a statement by the U.S. Central Command.
September 2014
By early September, according to Business Insider, Iranian Quds Force personnel were deployed to Samarra, Baghdad, Karbala, and the former U.S. military post known as Camp Speicher.
In late September, Iranian general Ahmad Reza Pourdastan threatened to "attack deep into Iraqi territory" should ISIL forces approach the Iranian border. Earlier in the month, the Iranian government announced it had arrested Afghan and Pakistani nationals attempting to "cross Iran" to join ISIL.
There have been sporadic reports of ISIL troops in Iranian Kurdistan. These claims are unverified.
October 2014
Iranian general Qasem Soleimani, chief of the Iranian Quds Force, was reportedly present on the battlefield during Operation Ashura. In early October, the Islamic Republic of Iran News Network (IRINN) published a picture of Soleimani, purportedly on some battlefield alongside Kurdish Peshmerga. The Operation Ashura included Shi'ite paramilitary groups such as Asa'ib Ahl al-Haq, Kata'ib Hezbollah and the Badr brigades along with their leader Hadi Al-Amiri. Hezbollah was also present to provide technical advice and combat support for the allied offensive against the town of Jurf al-Sakhr.
November 2014
On 14 November, it was reported that the army had taken full control of Baiji, forcing ISIL forces to withdraw, and on 18 November, the anti-terrorism force Mosul Battalion entered the refinery for the first time since June. However, this could not be confirmed independently. If confirmed, it would be a major victory for Iraqi forces. State television said that they had entered the gates of the refinery. Meanwhile, it was confirmed that Iraqi forces were in full control of Baiji. Iraqi state television said Baiji's recapture was a "Graveyard for ISIS". Later, the US Department of State congratulated the Iraqi forces for retaking the country's largest oil refinery, confirming the Iraqi victory.
At the end of November, according to the Israeli website Haaretz, Al Jazeera broadcast a video showing Iranian F-4 Phantom jet-fighters bombing ISIL targets in northeastern Iraq, though Al Jazeera, in its report, alleged they were "Iraqi jet-fighters". US rear Admiral John Kirby affirmed on 3 December that he had "indications that [Iran] did indeed fly air strikes with F-4 Phantoms" targeting ISIL positions in the eastern Iraqi province of Diyala.
December 2014
On 27 December, Iranian IRGC Brigadier General Hamid Taqavi was killed in Samarra, Iraq, reportedly by an ISIL sniper. He is the highest ranking Iranian military official to die in Iraq since Iran's military intervention began, other than Qasem Soleimani.
March–April 2015
On 2 March 2015, Iraqi forces and allied Shia militias launched an offensive to recapture Tikrit from ISIL. Qasem Soleimani, commander of Iran's Quds Force, was reported to be overseeing part of the operation. Iran supplied artillery and other weapons, while Iranian military advisers helped coordinate the offensive.
After the offensive stalled, the US-led coalition began airstrikes on 25 March at the Iraqi government's request. Kata'ib Hezbollah and Asa'ib Ahl al-Haq suspended their participation in protest, while the Badr Organization said it would continue fighting. The Iraqi government announced Tikrit's recapture on 31 March.
Jim Phillips of the American The Heritage Foundation in March described Suleimani's role in this war as: "he's Iran's viceroy for Iraq".
May 2015
Following ISIL's capture of Ramadi in May, the Iraqi government allowed Iranian-backed Shia militias to rejoin the fighting in the area. According to Iranian state media, IRGC commander Jassem Nouri was killed near Ramadi on 28 May while advising Iraqi forces.
September–October 2015
Iran, Iraq, Russia and Syria agreed in September to share intelligence on ISIL through a joint coordination center in Baghdad. On 16 October, Iraqi forces and allied Shia militias, including the Iranian-backed Badr Organization and Asa'ib Ahl al-Haq, recaptured the Baiji oil refinery from ISIL. Badr spokesman Karim al-Nuri and an Asa'ib Ahl al-Haq official told Reuters that an Iranian member of the Baghdad intelligence-sharing cell had assisted in the operation.