Almost three centuries had passed since Peroz, in his war against the Hephthalites, had set the seal on a disastrous reign with one final, calamitous battle. Much had changed since then, and yet the miseries suffered by Khorasan under Hisham and his successors had come to wear a very familiar look. As resentments and frustrations bred of heavy taxation gnawed at an oppressed population, so had Muslim armies beyond the Oxus suffered a series of humiliating reverses. Not even the ultimate stabilisation of Transoxiana could erase the notorious reputations of a succession of incompetent Umayyad governors. “You abandoned us like pieces of a slaughtered beast, cut up for a round-breasted girl,”84 the Arabs of the eastern front sang of one particularly epicene appointee from Damascus. Yet Umayyad authority was threatened by more than the resentments of Muslim settlers; it was in peril as well from the same traditions that had once blackened the name of Peroz. In Khorasan—where great Parthian dynasts such as the Karin still jealously guarded their prerogatives against the upstart Muslim elite, and where most towns and villages remained wholly untouched by Islam—it often seemed as though Iranshahr had never fallen. That the world was divided into rival spheres of good and evil; that a great monarch was either a defender of truth or he was nothing; that the wickedness of an oath-breaker would bring ruin to his realm: here were presumptions still widely taken for granted along the eastern marches of Iran. The result was, as Umayyad rule began to implode, that the stirrings of rebellion could be felt well beyond the Fertile Crescent. In 745, even as the Kharijites were launching their latest insurgency, a mysterious prophet appeared in Khorasan. Dressed all in green—the colour of Mihr—brandishing a book of revelations written in Persian, and proclaiming himself familiar with the byways of heaven, Bihafarid was a revolutionary conjured, it seemed, from the most haunting mists of the Iranian past. Having died and then risen again—or so his disciples proclaimed—he announced his mission in terms that nakedly scorned all the pretensions of Muhammad: “O people, I am Bihafarid, the Messenger of God!”85
Of course, it could not possibly last. Muslim rule, whatever the hopes of the great multitudes of peasants who flocked in excitement to Bihafarid’s banner, was not so easily overthrown. Sure enough, in 749, the self-proclaimed prophet was arrested, put in chains and hanged in a nearby mosque. Yet his executioners, for all that it would have appalled them to contemplate it, were not, perhaps, wholly dissimilar to the man they had put to death. Bihafarid’s murderers were themselves followers of an insurrectionist who had emerged abruptly on the fringes of the former Iranshahr, and combined charisma with a dramatic claim to be an agent of God. “Father of a Muslim,” he called himself: a name so obviously a pseudonym as to give away nothing at all. His glamour, in part at least, was that of a man in a mask. “The knowledge of my deeds,” as he put it with a calculated show of mystery, “is better for you than the knowledge of my pedigree.”86 Yet whether an Arab or an Iranian, an aristocrat or a former slave, one thing, at least, is certain: he was powerfully assisted in his preachings by the same identical swirl of yearnings and expectations as had inspired Bihafarid. Along the easternmost fringes of the Caliphate, faiths were not easily patrolled. So it had ever been, of course, in border zones. No wonder, then, far distant as they were from all the efforts of the ulama to raise barriers around the practice of their religion, that the Muslims of Khorasan should have betrayed the influence of beliefs older by far than the Sunna. What helped to give Abu Muslim his prestige among them was that he dared, as once the critics of Peroz had done, to damn their ruler as a man condemned by God. Although he did not, like Bihafarid, clothe himself in green, yet in the summer of 747, when he declared open rebellion against Marwan, he unfurled a banner dyed a single colour: black. That he did this in a village outside Merv, where the fugitive Yazdegird had been murdered, was hardly suggestive, of course, of any nostalgia on Abu Muslim’s part for the House of Sasan; and yet, to Iranians, his preachings might well have stirred memories of the toppled monarchy. The cause proclaimed by Abu Muslim was that of a single family, appointed by God to the rule of the world; and if the mark of their claim to this awesome status was the possession, not of a farr but rather of a bloodline traceable back to the uncle of the Prophet, then that, in an Islamic empire, promised qualification enough. Abu Muslim, like so many other rebels trained in subterfuge and insurrection, was an agent of the Abbasids; and by raising the East in their cause, he had succeeded in fusing the past with the future, the Iranian with the Arab, the Sasanian with the Islamic. It was to prove a quite staggeringly potent combination—and the ruin of the Umayyads.
The flames of rebellion swept westwards from Khorasan so fast and so ferociously that Marwan was caught out fatally short. Already, as the spring of 749 turned to summer, Abbasid forces had secured complete control of Iran. By August, they were across the Euphrates; by September, they were inside Kufa. On 28 November, in the very mosque where Ali had been murdered, an Abbasid was publicly hailed as Caliph. Marwan now had no option but to meet the provocation head on. Rather than wait for the full roster of his veterans to assemble, he opted instead to cobble together such units as were already available to him in Harran and lead them against the pretender. On 25 January 750, on the bank of a tributary of the Tigris called the Greater Zab, he spotted the black banners of the Abbasids, advanced, and fell upon the rebels. The result was calamity. His army was obliterated. As unyielding as ever, even in the face of such a disaster, the tireless Marwan fled the battlefield and desperately struggled to marshal further troops—but there were none to be found. Galloping past both Damascus—the capital he had abandoned—and Jerusalem—the city that now mocked his dynasty’s crumbled greatness more than any other—he made his way into Egypt. Here, in the heat of the summer, he was finally cornered by his pursuers. His head, topped by the frizz of his curly hair, was dispatched to his replacement upon the throne of the Caliphs. His tongue was fed to a cat.