The Iran-Iraq War (Referred to as قادسيّة صدّام "Saddām's Qādisiyyah" in Iraq, and جنگ تحمیلی "Iraqi Imposed War" in Iran) was a major war fought between the Islamic Republic of Iran and Ba'athist Iraq from 1980 to 1988.
The war began on September 22, 1980, when Iraqi armored forces crossed the border in to Iran, taking advantage of the turmoil caused by the Iranian Revolution. Though the Iraqi forces had the element of surprise, they were soon turned back by the Iranians. By mid-1982, Iraq had been forced to give up almost all of its initial territorial gains.
Iraq received much support from neighboring Arab Gulf states, mostly in the form of monetary loans. The most significant contributions included $30.9 billion from Saudi Arabia, $8.2 billion from Kuwait, and $8 billion from the United Arab Emirates.
Saddam Hussein expected these loans to be forgiven without repayment, leading to conflict when they were not. Most notably, tensions between Kuwait and Iraq lead to Hussein's 1990 invasion (see Invasion of Kuwait), among other factors.
The "Tanker War"
The United States had been at odds with Iran since the Iran Hostage Crisis. After Iranian and Iraqi forces both began attacking oil tankers from noncombatant nations, the US began to provide direct financial and military aid to Iraqi forces. In 1987, at the request of the Kuwaiti government, the U.S. initiated Operation Earnest Will, escorting neutral tankers through the battle zone. This led to a number of confrontations between U.S. and Iranian forces.
The war was marked by Saddam Hussein's use of chemical weapons against Iran and Kurdish populations in northern Iraq. The first use of chemical weapons was during an Iranian assault of Basra in 1982. The weapons were non-lethal, but succeeded in turning back an entire Iranian division. Subsequent attacks by the Iraqi forces involved mustard gas, nerve agents, and cyanide. Chemical attacks achieved varied levels of success during the war.
In 1987 and 1988, chemical weapons, including mustard gas, tabun nerve gas, and cyanide, were released on civilian populations in Kurdistan in punitive attacks to suppress Kurdish rebels and prevent them from collaborating with the Iranian forces. The attacks killed thousands and turned hundreds of thousands of Kurds into refugees. See: Operation Anfal.
As far as is known, Iranian forces never deployed chemical weapons, partly because the Iranians had nowhere near the capability the Iraqis had, and partly because Iran was hoping for a propaganda victory and international condemnation of the Iraqi government. Western response, however, was generally muted.
Years later, Hussein's use of chemical weapons against his own people were listed among the many reasons the United States began Operation Iraqi Freedom in 2003.
During the eight years of warfare, nearly 1,000,000 people lost their lives. The Iran-Iraq War was the first since World War I to see extensive use of chemical weapons, and the first since World War II to see such an intensive campaign against non-belligerent shipping. The war bankrupted the Iraqi economy, and the massive war debt was the main reason for the attempted Iraqi annexation of Kuwait in 1990, leading to the Gulf War.