The Iran-Iraq War (also called the First Persian Gulf War, or the Imposed War in Iran) was a war between Iran and Iraq, lasting from September 22, 1980 until August 20, 1988. The origins of the war are disputed, but was fundamentally a war over dominance in the Persian Gulf region. Rulers in both countries hoped to reduce the power of the other in order to bolster their own domestic and international power. The war began with an Iraqi invasion of Iran which advanced quickly, then stabilized into a defensive position for the bulk of the war, and then advanced again later in the war. It was commonly referred to outside the United States as the Persian Gulf War until the Iraq-Kuwait Conflict (1990-91), when that second conflict became known as the Persian Gulf War (aka Desert Storm or the commonly termed, though erroneous First Gulf War within the United States after the 2003 Invasion of Iraq).
One of the factors contributing to hostility between the two powers was Iraqi President Saddam Hussein's desire to regain full control of the Shatt al-Arab waterway at the head of the Persian Gulf, an important channel for the oil exports of both countries. In 1975, United States Secretary of State Henry Kissinger had sanctioned the Shah of Iran to attack Iraq over the waterway, which was then under Iraqi control at the time. Iran had also been supporting a Kurdish rebellions in Iraq. In 1975 Iran and Iraq signed the Algiers Accord in which Iraq made territorial concessions, including the waterway, in exchange for normalized relations between the two countries.
Following the February 1979 Islamic Revolution which overthrew the Shah, Iraq and some other Arab countries also feared the possible spread of the Islamic Revolution to their countries, that would put an end to their secular or Sunni dominated regimes. The Iranian regime disliked the secular Ba'athist regime in Iraq and did try to eliminate it. They funded Kurdish separatists in northern Iraq, and Shiite leaders in the rest of Iraq, hoping to cause a civil war, allowing the Shi'ite majority in Iraq to revolt against Hussein's Sunni dominated government.
Iraq also had designs on the Iranian province of Khuzestan, which is the main oil area in Iran. It is also speculated that he United States encouraged Hussein to attack Iran over this disputed waterway as a possible way of blunting and undermining the Iranian Revolution of 1979 which had eliminated U.S. influence in Iran.
Saddam had recently come to power and was interested in elevating Iraq to a regional superpower. A successful invasion of western Iran would make Iraq the sole dominating force in the Gulf region and its lucrative oil trade. Such lofty ambitions were not that farfetched. Severe officer purges and spare part shortages for Iran's American-made equipment had crippled Iran's once mighty military. The bulk of the Iranian military was made up of poorly armed, but committed militias. To top it off, Iran had minimal defenses in the Arvand river (Shatt al-Arab) area. On September 22, 1980, Iraq seized the opportunity and invaded, using the so-called Iran-backed assassination attempt aimed at then-Foreign Minister Tariq Aziz as a pretext for the attack.
Early on Iraq had great successes, advancing on a wide front into Iranian territory. However, the Iraqis soon found that the Iranian military was not nearly as depleted as they thought. The Iranian people rallied behind their new government to fight off the Iraqi invaders. In June, 1982, a successful Iranian counter-offensive recovered the areas previously lost to Iraq. Most of the fighting for the rest of the war occurred on Iraqi territory, although some have interpreted the Iraqi withdrawal as a tactical ploy by the Iraqi military. By fighting just inside Iraq, Saddam Hussein could rally popular Iraqi patriotism. The Iraqi army could also fight on its own territory and in well established defensive positions. The Iranians continued to employ unsophisticated human wave attacks while Iraqi defenders remained, for the most part in a defensive posture.
Iraq's army was primarily armed with weaponry it had purchased from the Soviet Union and her satellites in the preceding decade. During the war, it purchased more equipment from the Soviets and their allies, as well as from China, France, Egypt, maybe Germany, and other sources (including European facilities for making and/or enhancing chemical weapons). Much of Iraq's financial backing came from other Arab states, notably oil-rich Kuwait and Saudi Arabia. Starting in 1982 with Iranian success on the battle field, the United States changed its less announced policy of backing Iraq to a clear direct support, supplying it with weapons and economic aid, and normalizing relations with the government (broken during the 1967 Six-Day War).
Despite this, for a period starting in 1985, the United States sold weapons to Iran in addition to Iraq. This sparked the 1986-1988 Iran-Contra Affair in Washington.
The United States engaged in a series of naval battles with Iranian forces in 1987 and 1988. The U.S. cruiser USS Vincennes (July 3, 1988) shot down Iran Air Flight 655 with the loss of all 290 passengers and crew, including women and children. Some analysts interpreted this as a very severe warning to end the war, as it no longer benefited the U.S. government. The American Government said that the airliner had been mistaken for an Iranian F-14 Tomcat which had been in the same general area as the civilain plane shortly beforehand.
Iraq offered a cessation of hostilities in 1982 but Iran's insistence from July 1982 onward to destroy the Iraqi regime prolonged the conflict for another six years of static warfare. In the final years of the war Iraq received more and more foreign aid, and began to build a more modern, well trained army, air force, and navy. In 1988 Iraq launched another offensive into Iranian territory and began serious air attacks on Iranian cities such as Tehran. Iran felt militarily isolated and offered to open peace negotiations. Iraq accepted since the Iraqi economy and population had suffered from the war for 8 years, and Iraq's widespread use of chemical weapons made the Iranians fear for the safety of their cities they agreed to a truce.
The war was characterized by extreme brutality, including the use of chemical weapons, by both countries, and especially tabun, by Iraq. Very little pressure was brought upon Iraq by the world community to curb such attacks or to condemn its earlier initiation of hostilities. The tactics used in the war resembled those of World War I with costly human wave attacks commonly used by both sides.
The war was disastrous for both countries, stalling economic development and disrupting oil exports, and costing an estimated million lives. Iraq was left with serious debts to its former Arab backers, including $14 billion loaned by Kuwait (1), a debt which contributed to Saddam's 1990 decision to invade Kuwait.
Much of both sides oil industry was damaged. Air raids had been launched by both nations against the oil infrastructure.
The end of the war left the borders unchanged. Two years later, as war with the western powers loomed, Saddam recognised Iranian rights over the eastern half of the Shatt al-Arab, a reversion to the status quo which he had repudiated a decade earlier.
The war would be extremely costly, one of the deadliest wars since the Second World War in terms of casualties. Conflicts since 1945 which have surpassed the Iran-Iraq War in terms of casualties include the Vietnam War, Korean War, the Second Sudanese Civil War, the war in the Democratic Republic of the Congo, among others.