February 1979, Ayatollah (Shiite Muslim religious leader) Ruhollah Khomeini, the inspirational and spiritual leader of the revolution, returned from exile in France and set up a provisional government led by Prime Minister Mehdi Bazargan. After a brief period of armed resistance put up by royalist supporters, the revolution prevailed and Ayatollah Khomeini consolidated political power. Then, in a national referendum held in March 1979, Iranians overwhelmingly voted to abolish the monarchy (ending 2,500 years of monarchical rule) and allow the formation of an Islamic government. Then in November 1979, the Iranian people, in another referendum, adopted a new constitution that turned the country into an Islamic republic and raised Ayatollah Khomeini to the position of Iran’s Supreme Leader, i.e. head of state and the government’s highest ranking political, military, and religious authority. Prime Minister Bazargan, whose liberal democratic and moderate government had held only little power, resigned in November 1979. By February 1980, Iran had fully transitioned to a theocracy under Ayatollah Khomeini, with executive functions run by a subordinate civilian government led by President Abolhassan Banisadr.
(Taken from Iran-Iraq War – Wars of the 20th Century –Vol. 4)
The political unrest in Iran had been watched closely by Iraq, Iran’s neighbor to the west, and particularly by Saddam Hussein, the Iraqi dictator. In the period following the Iranian Revolution, relations between the two countries appeared normal, with Iraq even offering an invitation to new Iranian Prime Minister Bazargan to visit Iraq. But with Iran’s transition to a hard-line theocratic regime, relations between the two countries deteriorated, as Iran’s Islamist fundamentalism contrasted sharply with Iraq’s secular, socialist, Arab nationalist agenda.
This breakdown in relations was only the latest in a long history of Arab-Persian hostility that resulted from a complex combination of ethnic, sectarian, political, and territorial factors. During the period when the Ottoman Empire ruled over the Middle East (16th – 19th centuries, to early 20th century), the Ottoman Empire and Persian Empire fought for possession of sections of Mesopotamia, (present-day Iraq), including the Shatt el-Arab, the 200-kilometer long river that separates present-day southern Iraq and western Iran. In 1847, the Ottomans and Persians agreed to make the Shatt al-Arab their common border; the Persian Empire also was given control of Khoramshahr and Abadan, areas on its western shore of the river that had large Arab populations.
Then in 1937, the now independent monarchies of Iraq and Iran signed an agreement that stipulated that their common border on the Shatt al-Arab was located at the low water mark on the eastern (i.e. Iranian) side all across the river’s length, except in the cities of Khoramshahr and Abadan, where the border was located at the river’s mid-point. In 1958, the Iraqi monarchy was overthrown in a military coup. Iraq then formed a republic and the new government made territorial claims to the western section of the Iranian border province of Khuzestan, which had a large population of ethnic Arabs.
In Iraq, Arabs comprise some 70% of the population, while in Iran, Persians make up perhaps 65% of the population (an estimate since Iran’s population censuses do not indicate ethnicity). Iran’s demographics also include many non-Persian ethnicities: Azeris, Kurds, Arabs, Baluchs, and others, while Iraq’s significant minority group comprises the Kurds, who make up 20% of the population. In both countries, ethnic minorities have pushed for greater political autonomy, generating unrest and a potential weakness in each government of one country that has been exploited by the other country.
The source of sectarian tension in Iran-Iraq relations stemmed from the Sunni-Shiite dichotomy. Both countries had Islam as their primary religion, with Muslims constituting upwards of 95% of their total populations. In Iran, Shiites made up 90% of all Muslims (Sunnis at 9%) and held political power, while in Iraq, Shiites also held a majority (66% of all Muslims), but the minority Sunnis (33%) led by Saddam and his Baath Party held absolute power.
In the 1960s, Iran, which was still ruled by a monarchy, embarked on a large military buildup, expanding the size and strength of its armed forces. Then in 1969, Iran ended its recognition of the 1937 border agreement with Iraq, declaring that the two countries’ border at the Shatt al-Arab was at the river’s mid-point. The presence of the now powerful Iranian Navy on the Shatt al-Arab deterred Iraq from taking action, and tensions rose.