The Iran–Iraq War followed a long-running history of territorial border disputes between the two states, as a result of which Iraq planned to retake the eastern bank of the Shatt al-Arab that it had ceded to Iran in the 1975 Algiers Agreement.

[63] Of Iraq's six divisions that invaded by ground, four were sent to Khuzestan, which was located near the border's southern end, to cut off the Shatt al-Arab[note 5] from the rest of Iran and to establish a territorial security zone.

[63]: 22  On the central front, the Iraqis occupied Mehran, advanced towards the foothills of the Zagros Mountains, and were able to block the traditional Tehran–Baghdad invasion route by securing territory forward of Qasr-e Shirin, Iran.

Saddam was given diplomatic, monetary, and military support by the United States, including massive loans, political influence, and intelligence on Iranian deployments gathered by American spy satellites.

[133] With Iranian success on the battlefield, the United States increased its support of the Iraqi government, supplying intelligence, economic aid, and dual-use equipment and vehicles, as well as normalizing its intergovernmental relations (which had been broken during the 1967 Six-Day War).

[87][141] At a cabinet meeting in Baghdad, Minister of Health Riyadh Ibrahim Hussein suggested that Saddam could step down temporarily as a way of easing Iran towards a ceasefire, and then afterwards would come back to power.

Iraq used newly acquired T-55, T-62 and T-72 tanks, as well as Chinese copies, BM-21 truck-mounted rocket launchers, and Mi-24 helicopter gunships to prepare a Soviet-type three-line defence, replete with obstacles such as barbed wire, minefields, fortified positions and bunkers.

[125] They planned to take the Iraqis by surprise using Basij militiamen, army helicopters, and some armoured forces, then stretch their defences and possibly break through them to open a road to Baghdad for future exploitation.

[125] During Operation Muslim ibn Aqil (1–7 October),[note 7] Iran recovered 150 km2 (58 sq mi) of disputed territory straddling the international border and reached the outskirts of Mandali before being stopped by Iraqi helicopter and armoured attacks.

[101] They wanted to drive Iraq into economic failure by wasting money on weapons and war mobilization, and to deplete their smaller population by bleeding them dry, in addition to creating an anti-government insurgency.

[103] Iranian military advisors organised the Kurds into raiding parties of 12 guerrillas, which would attack Iraqi command posts, troop formations, infrastructure, including roads and supply lines, and government buildings.

[60][155] On the night of 10–11 February 1986, the Iranians launched Operation Dawn 8,[171] in which 30,000 troops in five Army divisions and men from the Revolutionary Guard and Basij advanced in a two-pronged offensive to capture the al-Faw peninsula in southern Iraq, the only area touching the Persian Gulf.

In one attack, Tehran's main oil refinery was hit, and in another instance, Iraq damaged Iran's Assadabad satellite dish, disrupting Iranian overseas telephone and telex service for almost two weeks.

The Iranians had withdrawn their remaining soldiers to Khuzestan in fear of a new Iraqi invasion attempt, allowing the Mujahedeen to advance rapidly towards Kermanshah, seizing Qasr-e Shirin, Sarpol-e Zahab, Kerend-e Gharb, and Islamabad-e-Gharb.

Using 60,000 troops along with helicopter gunships, chemical weapons (poison gas), and mass executions, Iraq hit 15 villages, killing rebels and civilians, and forced tens of thousands of Kurds to relocate to settlements.

[178][195] At the war's conclusion, it took several weeks for the Armed Forces of the Islamic Republic of Iran to evacuate Iraqi territory to honor pre-war international borders set by the 1975 Algiers Agreement.

[46] According to the Janbazan Affairs Organization, 398,587 Iranians sustained injuries that required prolonged medical and health care following primary treatment, including 52,195 (13%) injured due to the exposure to chemical warfare agents.

To enforce payment, Iraq was put under a comprehensive international embargo, which further strained the Iraqi economy and pushed its external debt to private and public sectors to more than $500 billion by the end of Saddam's rule.

In January 1985, former prime minister and anti-war Islamic Liberation Movement co-founder Mehdi Bazargan criticised the war in a telegram to the United Nations, calling it un-Islamic and illegitimate and arguing that Khomeini should have accepted Saddam's truce offer in 1982 instead of attempting to overthrow the Ba'ath.

[225] The Iranian government-owned Etelaat newspaper wrote, "There is not a single school or town that is excluded from the happiness of 'holy defence' of the nation, from drinking the exquisite elixir of martyrdom, or from the sweet death of the martyr, who dies in order to live forever in paradise.

Following Iran's success in repelling the Iraqi invasion and Khomeini's refusal to end the war in 1982, the United States made an outreach to Iraq, beginning with the restoration of diplomatic relations in 1984.

[236] The United States pursued policies in favour of Iraq by reopening diplomatic channels, lifting restrictions on the export of dual-use technology, overseeing the transfer of third-party military hardware, and providing operational intelligence on the battlefield[citation needed].

Turkey took action against the Kurds in 1986, alleging they were attacking the Kurdistan Workers' Party (PKK), which prompted a harsh diplomatic intervention by Iran, which planned a new offensive against Iraq at the time and were counting on the support of Kurdish factions.

[129] The Iraqgate scandal revealed that a branch of Italy's largest bank, Banca Nazionale del Lavoro (BNL), in Atlanta, Georgia, relied partially on U.S. taxpayer-guaranteed loans to funnel $5 billion to Iraq from 1985 to 1989.

[249] American support for Ba'athist Iraq during the Iran–Iraq War, in which it fought against post-revolutionary Iran, included several billion dollars' worth of economic aid, the sale of dual-use technology, non-U.S. origin weaponry, military intelligence, and special operations training.

[279] In response to further Iraqi chemical attacks on Kurdish civilians after the August 1988 ceasefire with Iran, United States senators Claiborne Pell and Jesse Helms called for comprehensive economic sanctions against Iraq, including an oil embargo and severe limitations on the export of dual-use technology.

[117] According to journalist Robin Wright: During the Fateh offensive in February 1987, I toured the southwest front on the Iranian side and saw scores of boys, aged anywhere from nine to sixteen, who said with staggering and seemingly genuine enthusiasm that they had volunteered to become martyrs.

[293] The Iran–Iraq War is regarded as being a major trigger for rising sectarianism in the region, as it was viewed by many as a clash between Sunni Muslims[294][295][296] (Ba'athist Iraq and other Arab States) and the Shia revolutionaries that had recently taken power in Iran.

[303] State media in Iraq dubbed the war Saddam's Qadisiyyah (قادسية صدام, Qādisiyyat Ṣaddām), in reference to the seventh-century Battle of al-Qādisiyyah, in which Arab warriors overcame the Sasanian Empire during the Muslim conquest of Iran.

[304] "We are armed with Allahu Akbar", the 1979 Iranian Islamic revolutionary military march song performed by IRGC troops in front of Ayatollah Khomeini in Jamaran Husinie, made a cultural impact during the war.