During the last days of the Umayyad caliphate, Abu al-‘Abbās and his clan chose to begin their rebellion in Khurasān, an important, but remote military region comprising eastern Iran, southern parts of the modern Central Asian republics of Turkmenistan, Uzbekistan, Tajikistan, Kyrgyzstan and northern Afghanistan. In 743, the death of the Umayyad Caliph Hishām provoked a rebellion in the east. Abu al-`Abbās, supported by Shi'as and the residents of Khurasān, led his forces to victory over the Umayyads. The civil war was marked by millennial prophecies encouraged by the beliefs of some Shi'as that As-Saffāḥ was the "mahdi." In Shi'ite works such as the "Al-Jafr" faithful Muslims were told that the brutal civil war was the great conflict between good and evil. The choice of the Umayyads to enter battle with white flags and the Abbasids to enter with black encouraged such theories. The color white, however, was regarded in much of Persia as a sign of mourning.