What is the reason behind the Iran-Iraq war in the 80s?how it started and why?

Answer 1

They had nothing better to do.

Answer 2

to stole oil

Answer 3

Reason for Iran Iraq war:
The Iran-Iraq War, also known as the Imposed War (جنگ تحمیلی, Jang-e-tahmÄ«lÄ«) in Iran, and Saddām's Qādisiyyah (قادسيّة صدّام, Qādisiyyat Saddām) in Iraq, was a war between the armed forces of Iraq and Iran lasting from September 1980 to August 1988. It was commonly referred to as the (Persian) Gulf War until the Iraq-Kuwait conflict (1990–91), which became known as the Second (Persian) Gulf War and later simply the (Persian) Gulf War.

It has been called "the longest conventional war of the 20th century", and cost 1 million casualties and US$1.19 trillion. (D. Hiro)

The war began when Iraq invaded Iran on 22 September 1980 following a long history of border disputes, demands for the overthrow of Saddam Hussein's regime, and secret encouragement by the US administration (Jimmy Carter, conveyed through Saudi Arabia) which was embroiled in a dispute with the new regime in Iran.

The conflict saw early successes by the Iraqis, but before long they were repelled and the conflict stabilized into a long war of attrition. The United Nations Security Council called upon both parties to end the conflict on multiple occasions, but a ceasefire was not agreed to until 20 August 1988, and the last prisoners of war were not exchanged until 2003. The war irrevocably altered politics in the area, playing into wider global politics and leading to the 1990 Iraqi invasion of Kuwait.

The war is also noted for extensive use of chemical weapons by Iraqi forces, although it is possible, but not comfirmed, that Iranian forces also deployed such weapons.
Although the Iran-Iraq war of 1980–1988 was a war over dominance of the Persian Gulf region, the roots of the war go back many centuries. There has always been a rivalry between various kingdoms of Mesopotamia (modern Iraq) and Persia (Iran).

Before the Ottoman empire, Iraq was part of Persia ruled under the Aq Qoyunlu dynasty. The rising power of the Ottomans put an end to this when Murad IV annexed what is today Iraq from the weakening Safavids of Persia in 1638. The border disputes between Persia and the Ottomans never ended however. Between 1555 and 1918, Persia and the Ottoman empire signed no less than 18 treaties re-addressing their disputed borders. Modern Iraq was created with the British involvement in the region and the final collapse of the Ottoman empire, hence inheriting all the disputes with Persia.

More precisely, the origins of the Iran-Iraq war of 1980–1988 go back to the question of sovereignty over the resource-rich province of Khuzestan. Khuzestan, home to Iran's Elamite Empire, was an independent non-Semitic speaking kingdom whose capital was Susa. Khuzestan has, however, been attacked and occupied by various kingdoms of Mesopotamia (the precursors of modern Iraq) many times.

On 18 December 1959, `Abd al-Karīm Qāsim, who had just taken control over Iraq by a coup d'état, openly declared: "We do not wish to refer to the history of Arab tribes residing in Al-Ahwaz and Mohammareh [Khorramshahr]. The Ottomans handed over Mohammareh, which was part of Iraqi territory, to Iran." The Iraqi regime's dissatisfaction over Iran's possession of oil-rich Khuzestan province was not limited to rhetorical statements; Iraq started supporting secessionist movements in Khuzestan, and even raised the issue of its territorial claims in the next meeting of the Arab League, without any success. Iraq showed reluctance in fulfilling existing agreements with Iran, especially after the death of Egyptian President Gamāl `Abd an-Nāsir and the rise of the Ba`ath Party, when Iraq decided to take on the role of "leader of the Arab world".

In 1969, the deputy prime minister of Iraq openly declared: "Iraq's dispute with Iran is in connection with Arabistan (Khuzestan) which is part of Iraq's soil and was annexed to Iran during foreign rule." Soon Iraqi radio stations began exclusively broadcasting into "Arabistan", encouraging Arabs living in Iran and even Balūchīs to revolt against Iran's central government. Basra TV stations even started showing Iran's Khuzestan province as part of Iraq's new province called 'Nasiriyyah', renaming all Iranian cities with Arabic names.

In 1971, Iraq broke off diplomatic relations with Iran after claiming sovereignty rights over the islands of Abu Musa, Greater Tunb and Lesser Tunb in the Persian Gulf, following the withdrawal of the British. Iraq then expelled 70,000 Iranians from its territory after complaining to the Arab League, and the UN, without any success.

One of the factors contributing to hostility between the two powers was a dispute over full control of the Arvandrud/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 that Mohammad Rezā' Pahlavī, the Shah of Iran, attack Iraq over the waterway, which was under Iraqi control at the time; soon afterward both nations signed the Algiers Accord, in which Iraq made territorial concessions, including the waterway, in exchange for normalized relations.

Iraq had staged a battle against Iranian forces a year earlier in 1974, resulting in heavy casualties on both sides. Iran attempted to destabilize Iraq and encouraged Kurdish nationalists to break up the country, in answer to Iraq's similar activities in Iran's Khuzestan province. Iran's embassy in London was subsequently attacked by Iraqi-sponsored terrorist forces a few months prior to the war in 1980, in what came to be known as The Iranian Embassy Siege.

Saddam Hussein, Iraq's president at that time, was eagerly interested in elevating Iraq to a strong regional power. A successful invasion of Iran would make Iraq the dominant power in the Persian Gulf region and strengthen its lucrative oil trade. Such lofty ambitions were not that far-fetched. Severe officer purges (including several executions ordered by Sādeq Khālkhālī, the post-revolution sharī`ah ruler) 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, though committed, militias. Iran had minimal defenses in the Arvand/Shatt al-`Arab river.

Saddām on numerous occasions alluded to the Islamic conquest of Iran in propagating his anti-Persian position against Iran. For example, on 02 April 1980, a half-year before the outbreak of the war, in a visit by Saddām to al-Mustansiriyyah University in Baghdad, drawing parallels to the 7th-Century defeat of Persia in the Battle of al-Qādisiyyah he announced:

"In your name, brothers, and on behalf of the Iraqis and Arabs everywhere we tell those [Persian] cowards and dwarfs who try to avenge Al-Qadisiyah that the spirit of Al-Qadisiyah as well as the blood and honor of the people of Al-Qadisiyah who carried the message on their spearheads are greater than their attempts." (See Saddām, E3)

The aftermath of the Iranian Revolution of 1979 was central to the conflict. The Āyat-Allāh Rūh-Ollāh Khomaynī was threatening to export Islamic revolution to the rest of the Middle East, even though Iran was hardly in any position to do so militarily, for most of the Shah's army had already been disbanded. The Khomeinist camp despised Iraq's Ba`athist secularism in particular, and believed that the oppressed Shī`īs in Iraq, Saudi Arabia, and Kuwait could follow the Iranian example and turn against their governments. At the same time the revolution in Iran, the destabilization of the country and its alienation from the West made it a tempting target to the expansionist Saddām Hussein. In particular he felt that Iranian Sunni citizens would rather join a powerful Sunni-led Iraq than remain in the Shia dominated Iran.

Thus Iraq entered the war believing that Sunnīs of Iran would join the opposing forces. It seems that Saddam hadn't fully appreciated the powers of nationalism over historically clan-centered differences, nor the power of the central state apparatus who controlled the press. Although some of the ethnic arabs of Khuzestan collaborated with Iraqis, most of the Sunnīs of Iran turned against Iraqi invaders.

The UN Secretary General report dated 9 December 1991 (S/23273) explicitly cites "Iraq's aggression against Iran" in starting the war and breaching International security and peace.