Some of the earliest known human settlements have been found in present-day Iraq. Habitations, shrines, implements, and pottery found on various sites can be dated as early as the 5th millennium BC . Some sites bear names that are familiar from the Bible, which describes the region of the Hiddekel (Tigris) and Euphrates rivers as the location of the Garden of Eden and the city of Ur as the birthplace of the patriarch Abraham. Scientific exploration and archaeological research have amplified the biblical accounts.
Recorded history in Mesopotamia (the ancient name of Iraq, particularly the area between the Tigris and Euphrates) begins with the Sumerians, who by the 4th millennium BC had established city-states. Records and accounts on clay tablets prove that they had a complex economic organization before 3200 BC . The reign of Sumer was challenged by King Sargon of Akkad (r.c.2350 BC ); a Sumero-Akkadian culture continued in Erech (Tall al-Warka') and Ur (Tall al-Muqayyar) until it was superseded by the Amorites or Babylonians (about 1900 BC ), with their capital at Babylon. The cultural height of Babylonian history is represented by Hammurabi (r.c.1792–c.1750 BC ), who compiled a celebrated code of laws. After Babylon was destroyed by the Hittites about 1550 BC , the Hurrians established the Mitanni kingdom in the north for about 200 years, and the Kassites ruled for about 400 years in the south.
From Assur, their stronghold in the north, the Assyrians overran Mesopotamia about 1350 BC and established their capital at Nineveh (Ninawa). Assyrian supremacy was interrupted during the 11th and 10th centuries BC by the Aramaeans, whose language, Aramaic, became a common language in the eastern Mediterranean area in later times. Assyrian power was finally crushed by the Chaldeans or Neo-Babylonians, who, in alliance with the Medes in Persia, destroyed Nineveh in 612 BC . Nebuchadnezzar II (r.c.605–c.560 BC ) rebuilt the city-state of Babylon, but it fell to the Persians, under Cyrus of the Achaemenid dynasty, in 539 BC . Under his son Cambyses II, the Persian Empire extended from the Oxus (Amu Darya) River to the Mediterranean, with its center in Mesopotamia. Its might, in turn, was challenged by the Greeks. Led by the Macedonian conqueror Alexander the Great, they defeated the Persians by 327 BC and penetrated deep into Persian lands. The Seleucids, Alexander's successors in Syria, Mesopotamia, and Persia, built their capital, Seleucia, on the Tigris, just south of Baghdad. They had to yield power to the Parthians, who conquered Mesopotamia in 138 BC .
The Arabs conquered Iraq in AD 637. For a century, under the "Orthodox" and the Umayyad caliphs, Iraq remained a province of the Islamic Empire, but the 'Abbasids (750–1258) made it the focus of their power. In their new capital, Baghdad, their most illustrious member, Harun al-Rashid (ar-Rashid, r.786–809), became, through the Arabian Nights, a legend for all time. Under Harun and his son Al-Ma'mun, Baghdad was the center of brilliant intellectual and cultural life. Two centuries later, the Seljuk vizier Nizam al-Mulk established the famous Nizamiyah University, one of whose professors was the philosopher Al-Ghazali (Ghazel, d.1111). A Mongol invasion in the early 13th century ended Iraq's flourishing economy and culture. In 1258, Genghis Khan's grandson Hulagu sacked Baghdad and destroyed the canal system on which the productivity of the region had depended. Timur, also known as Timur Lenk ("Timur the Lame") or Tamerlane, conquered Baghdad and Iraq in 1393. Meanwhile, the Ottoman Turks had established themselves in Asia Minor and, by capturing Cairo (1517), their sultans claimed legitimate succession to the caliphate. In 1534, Süleyman the Magnificent conquered Baghdad and, except for a short period of Persian control in the 17th century, Iraq remained an Ottoman province until World War I.
Late in 1914, the Ottoman Empire sided with the Central Powers, and a British expeditionary force landed in Iraq and occupied Basra. The long campaign that followed ended in 1918, when the whole of Iraq fell under British military occupation. The collapse of the Ottoman Empire stimulated Iraqi hopes for freedom and independence, but in 1920, Iraq was declared a League of Nations mandate under UK administration. Riots and revolts led to the establishment of an Iraqi provisional government in October 1920. On 23 August 1921, Faisal I (Faysal), the son of Sharif Hussein (Husayn ibn-'Ali) of Mecca, became king of Iraq. In successive stages, the last of which was a treaty of preferential alliance with the United Kingdom (June 1930), Iraq gained independence in 1932 and was admitted to membership in the League of Nations.
Faisal died in 1933, and his son and successor, Ghazi, was killed in an accident in 1939. Until the accession to the throne of Faisal II, on attaining his majority in 1953, his uncle 'Abdul Ilah, Ghazi's cousin, acted as regent. On 14 July 1958, the army rebelled under the leadership of Gen. 'Abd al-Karim al-Qasim (Kassim). Faisal II, Crown Prince 'Abdul Ilah, and Prime Minister Nuri al-Sa'id (as-Sa'id) were killed. The monarchy was abolished, and a republic established. Iraq left the anti-communist Baghdad Pact, which the monarchy had joined in 1955. An agrarian reform law broke up the great landholdings of feudal leaders, and a new economic development program emphasized industrialization. In spite of some opposition from original supporters and political opponents, tribal uprisings, and several attempts at assassination, Qasim managed to remain the head of Iraq for four and a half years. On 9 February 1963, however, a military junta , led by Col. 'Abd as-Salam Muhammad 'Arif, overthrew his regime and executed Qasim.
Since 1961, Iraq's Kurdish minority has frequently opposed with violence attempts by Baghdad to impose authority over its regions. In an attempt to cope with this opposition, the Bakr government passed a constitutional amendment in July 1970 granting limited political, economic, and cultural autonomy to the Kurdish regions. But in March 1974, Kurdish insurgents, known as the Pesh Merga, again mounted a revolt, with Iranian military support. The Iraqi army countered with a major offensive. On 6 March 1975, Iraq and Iran concluded an agreement by which Iran renounced support for the Kurds and Iraq agreed to share sovereignty over the Shatt al-'Arab estuary. The new regime followed a policy based on neutralism and aimed to cooperate with Syria and Egypt and to improve relations with Turkey and Iran. These policies were continued after 'Arif was killed in an airplane crash in 1966 and was succeeded by his brother, 'Abd ar-Rahman 'Arif. This regime, however, was overthrown in July 1968, when General (later Marshal) Ahmad Hasan al-Bakr, heading a section of the Ba'ath Party, staged a coup and established a new government with himself as president. In the 1970s, the Ba'ath regime focused increasingly on economic problems, nationalizing the petroleum industry in 1972–73 and allocating large sums for capital development. Bakr resigned in July 1979 and was followed as president by his chosen successor, Saddam Hussein (Husayn) al-Takriti.
Tensions between Iraq and Iran rose after the Iranian revolution of 1979 and the accession to power of Saddam Hussein. In September 1980, Iraq sought to take advantage of the turmoil in Iran by suddenly canceling the 1975 agreement and mounting a full-scale invasion. Iraqi soldiers seized key points in the Khuzistan region of southwestern Iran, captured the major southern city of Khorramshahr, and besieged Abadan, destroying its large oil refinery. The Iraqi army then took up defensive positions, a tactic that gave the demoralized Iranian forces time to regroup and launch a slow but successful counterattack that retook Khuzistan by May 1982. Iraq then sought peace and in June withdrew from Iranian areas it had occupied. Iran's response was to launch major offensives aimed at the oil port of Basra. Entrenched in well-prepared positions on their own territory, Iraqi soldiers repelled the attacks, inflicting heavy losses, and the war ground to a stalemate, with tens of thousands of casualties on each side.
Attempts by the UN and by other Arab states to mediate the conflict were unsuccessful; in the latter stages of the war, Iraq accepted but Iran regularly rejected proposals for a compromise peace. Although most Arab states supported Iraq, and the Gulf oil states helped finance Iraqi military equipment, the war had a destabilizing effect both on the national economy and on the ruling Ba'ath Party. France also aided Iraq with credits to buy advanced weapons (notably, Super Étendard fighters and Exocet missiles), and it provided the technology for Iraq to construct the Osirak nuclear reactor near Baghdad. (In June 1981, this installation was destroyed in a bombing raid by Israel, which claimed that the facility would be used to produce nuclear weapons, a charge Iraq denied.) Other Western countries provided supplies, financing, and intelligence to Iraq but denied the same to Iran.
In February 1986, the Iranians made their biggest gain in the war, crossing the Shatt al-'Arab and capturing Fao (Al-Faw) on the southernmost tip of land in Iraq. In early 1987, they seized several islands in the Shatt al-'Arab opposite Basra. The war soon spread to Persian Gulf shipping, as both sides attacked oil tankers and ships transporting oil, goods, and arms to the belligerents or their supporters.
The war ended on 20 August 1988 after Iran accepted a UN cease-fire proposal on 18 July. Having suffered enormous casualties and physical damage plus a massive debt burden, Baghdad began the postwar process of reconstruction. Before and after the war, there were scores to settle, primarily against the Kurds, some of whom had helped Iran and were the victims of Iraqi poison gas attacks. Many border villages were demolished and their Kurdish populations relocated.
When Iraq's wartime allies seemed unwilling to ease financial terms or keep oil prices high and questioned Iraq's rearmament efforts, Saddam Hussein turned bitterly against them. Kuwait was the principal target. After threats and troop movements, Iraq reasserted its claim (which dated from the days of the monarchy) to that country and on 2 August 1990, invaded and occupied it. Saddam Hussein was unflinching in the face of various peace proposals, economic sanctions, and the threatening buildup of coalition forces led by the United States.
A devastating air war led by the United States began on 17 January 1991 followed by ground attack on 24 February. Iraq was defeated, but not occupied. Despite vast destruction and several hundred thousand casualties, Saddam's regime remained firmly in control. It moved to crush uprisings from the Shia in the south and Kurds in the north. To protect those minorities, the United States and its allies imposed no-fly zones that gave the Kurds virtually an independent state, but afforded much less defense for the rebellious Arabs in the south whose protecting marshes were being drained by Baghdad. There were several clashes between allied and Iraq forces in both areas.
In 1996, in an effort to boost morale in Iraq and bolster its image abroad, Iraq conducted its first parliamentary elections since 1989. However, only candidates loyal to Saddam Hussein were allowed to run. A government screening committee reviewed and approved all 689 candidates, who either belonged to Hussein's Ba'ath Party or were independents who supported the 1968 coup that brought the party to power.
The Iraqi economy continued to decline throughout the 1990s, with the continuation of the UN sanctions, imposed in 1990, which prohibited Iraq from selling oil on the global market in major transactions and froze Iraqi assets overseas. The deteriorating living conditions imposed on the Iraqi population prompted consideration of emergency measures. In 1996 talks were held between Iraq and the United Nations on a proposed "oil for food" humanitarian program that would permit Iraq to sell a limited quantity of oil in order to purchase food and basic supplies for Iraqi citizens. The United States and Britain wanted money earmarked for Iraq's Kurdish provinces funneled through the existing United Nations assistance program there. They also raised the issue of equity with respect to Iraq's existing rationing system. In December 1996, the UN agreed to allow Iraq to export $2 billion in oil to buy food and medical supplies. Iraq began receiving 400,000 tons of wheat in the spring of 1997.
Since the end of the Gulf War, Iraq had demonstrated cooperation with UNSCOM, the special UN commission charged with monitoring weapons of mass destruction. However, Saddam Hussein refused to dismantle his country's biological weapons and had stopped cooperating with UNSCOM by August 1997, leading to increasing tension and a US military buildup in the region by early 1998. Personal intervention by UN Secretary General Kofi Annan helped diffuse the situation temporarily. However, renewed disagreements arose in the latter half of the year, ultimately leading to a December bombing campaign (Operation Desert Fox) by US and UK forces, with the goal of crippling Iraq's weapons capabilities. In late 1998 the US Congress also approved funding for Iraqi opposition groups, in hopes of toppling Saddam Hussein politically from within.
In 1999 the oil for food program was expanded to allow for the sale of $5.25 billion in oil by Iraq over a six-month period to buy goods and medicine. As of 2000, most observers agreed that the decade-long UN sanctions, while impoverishing Iraq and threatening its population with a major humanitarian crisis, had failed in their goal of weakening Saddam's hold on power.
The situation in Iraq intensified in 2002. In his January 2002 State of the Union Address, US president George W. Bush labeled Iraq, along with Iran and North Korea, part of an "axis of evil"—states that threatened the world with weapons of mass destruction and sponsored terrorism. Throughout 2002, the United States, in partnership with the UK, brought the issue of the need to disarm the Iraqi regime of weapons of mass destruction (WMD) to the forefront of international attention. On 8 November 2002, the UN Security Council unanimously approved Resolution 1441, calling upon Iraq to disarm itself of all biological, chemical, and nuclear weapons and weapons capabilities, to allow for the immediate return of UN and International Atomic Energy Agency (IAEA) weapons inspectors (they had been expelled from the country in 1998), and to comply with all previous UN resolutions regarding the country since the end of the Gulf War in 1991. UN and IAEA weapons inspectors returned to Iraq, but the United States and UK were neither satisfied with their progress nor with Iraq's compliance with the inspectors. The United States and the United Kingdom began a military buildup in the Persian Gulf region (eventually 250,000 US and 45,000 British troops would be stationed there), and pressed the UN Security Council to issue another resolution authorizing the use of force to disarm the Iraqi regime. This move was met by stiff opposition from France, Germany, and Russia (all members of the Security Council at the time, with France and Russia being permanent members with veto power); the diplomatic impasse ended on 17 March 2003, when the United States, the United Kingdom, and Spain withdrew from the Security Council the resolution they had submitted that February that would have authorized the use of military force. War began on 19 March 2003, and by early April, the Iraqi regime had fallen.
The post-war period proved to be a difficult one for the United States and the United Kingdom, as their troops attempted to prevent looting and violence, to disarm Iraqis, and to begin the process of reconstruction. Especially contentious was the issue of the formation of a new Iraqi government: Iraqi exiles returned to the country, attempting to take up positions of power; Kurds demanded representation in a new political structure; and Shi'ites (who make up some 60% of the Iraqi population), agitated for recognition and power. The United States initially installed retired US Army Lt. Gen. Jay Garner as head of the Office of Reconstruction and Humanitarian Assistance, to oversee Iraq's civil administration while a new government was to be installed. Garner was replaced by former US State Dept. official L. Paul Bremer III in May 2003 in what some called an effort to put a civilian face on the reconstruction effort. European and Arab states called upon the United States and the United Kingdom to provide for a central role to be played by the UN in reconstructing Iraq, but the scope of that role was undefined as of June 2003. Many Iraqi political figures in June labeled the allied campaign to remove the Saddam Hussein regime more like an "occupation" than a "liberation," and called for elections to a national assembly that would produce a new constitution for the country.