Five to ten thousand armed Iraqi Shi’ites, organized in small bands and recruited from refugees expelled by the Ba’th during the late 1970′s and 1980′s, entered the country through the marshlands around Basra on the second or third day of the uprising. They were units from the Badr Brigade, organized by the Supreme Islamic Council headed by Muhammad Baqir al-Hakim. [..] The first action of these angry young men pouring in from Iran seems to have been the storming of the Sheraton Hotel and the burning of the bars and casinos of the city of Basra. They then proclaimed the establishment of a Shi’i Islamic Republic in Basra. Surrendering or captured army personnel were executed, occasionally in “trials” presided over by clerics. These judgments were implemented on men who were in the eyes of the rebels “enemies of God”. [..]

Such violence, justified in the name of Islam, but more often than not motivated by the desire for vengeance, promptly terminated the lifeblood of the intifada: the flow of defections from the army. This explains the ability of the regime to regroup its shattered forces and strike back.  In Najaf, as we have seen, attempts were made to check the descent into anarchy by resident notables and ‘ulema‘, learned religious men, acting through the prestige of Ayatollah Khoei. But in Basra and Kerbala, whatever leadership there was came from Iraqis based in Tehran. These are also the cities where some of the worst rebel excesses occured.

- Kanan Makiya, Cruelty and Silence (1993)