(1980-1988)
In September 1980, Saddam Hussein's Iraq invaded Iran in the mistaken belief that Iran had been fatally weakened by its Islamic revolution. After initial Iraqi successes, the war bogged down into a long stalemate and thus created potential opportunities and dangers for the Kurdish national movements in both Iraq and Iran.
Both Iraq and Iran attempted to use each other's Kurds as fifth columns against the other. For their part, the Kurds attempted to win their national rights by supporting the enemy of the state in which they lived. Thus, the war set loose forces that enabled the Kurds to become more important international actors than they previously had been.
In Iraq, the Kurdistan Democratic Party (KDP) supported Iran from the very beginning. The Patriotic Union of Kurdistan (PUK), however, played a much more careful role, even for a while seeking to reach an understanding with Baghdad through the good offices of the Kurdistan Democratic Party of Iran (KDPI). It was not until 1987 that the KDP and PUK were able to bury the hatchet and—with Iran's help—announce in principle the creation of the Iraqi Kurdistan Front. This front became the seed of the de facto state of Kurdistan in northern Iraq following the Gulf War in 1991 and later the Kurdistan Regional Government (KRG).
The Iraqi Kurdish support for Iran, however, helped lead to Iraq's usage of chemical weapons against the Kurds in Halabja in March 1988 and the genocidal Anfal campaign to punish the Kurds. Maybe as many as 1,000,000 died in the Iran-Iraq War. At the war's end, the Kurds were definitely much worse off than they had been before the start of the war. On the other hand, the Iran-Iraq War also served to internationalize the Kurdish issue. The Gulf War three years later furthered this situation for the Iraqi Kurds, but the Iranian Kurds remained in a weakened position.
Historical Dictionary of the Kurds. Michael M. Gunter.