The domination of generals and governors was the last phase of the political evolution of the Sassanide period; but this new feudalism had no time to consolidate itself before the Arab invasion. In this eminently just dictum, Professor Christensen draws attention to the most important factor in the decline and fall of the Sassanide Empire. That feudalism, according to him, was the result of the military policy inaugurated under Khosro I (Anoshirvan the Just); for one result of that policy was that each Spahbod or governor considered his province as something like a hereditary fief.
Professor Christensen might have gone on to add that, with the decline of the old dynasty, such generals and governors were tempted more and more to play the part of king-makers, or to set up as kings themselves. For example, Bahram Chobin, Vistakhm (Bistam) and Farrukhan Shahrvaraz (Shahran-Guraz) made themselves kings with temporary success. The fatal example was set by Bahram Chobin and was followed by Shahran-Guraz with disastrous results for the unity and independence of old Iran. But the assassination of Shahran-Guraz convinced the nobles of the country that the game of usurping the throne was too dangerous, and one which the country, devoted as it was to the Sassanian dynasty, was not likely to tolerate. Thenceforward the aristocracy took up the plan of playing the part of king-makers. This accounts for the very large number of young kings, who were set up and dethroned after the reign of Shahran-Guraz. Even before that year under Ardeshir III, Mah-Adhur-Gushnasp had figured as the regent. Some time later Farrukh-Hormuzd who was the governor of Khorassan, according to Tabari, or the "ishkan" or prince of Azarbaijan, according to Armenian sources) aspired to the crown and attempted to secure it by proposing a marriage to queen Azarmidokht. The proud queen refused these overtures and got rid of her ambitious suitor by having him assassinated. However, Rustam, the son of Farrukh-Hormuzd, avenged his father by marching on the capital, seizing the queen and having her blinded and deposed. Both father and son have been styled "ishkans" or "princes” of Azarbaijan by Armenian writers. It would also appear that prince Rustam had the ambition of enlarging his realm by conquests. For we read in the Armenian history by M. St. Martin that Rustam conquered Armenia from its Byzantine governor Prince Varazdirot in A.D. 631. These Armenian conquests of Rustam might account for the fact that when he marshaled his army against the Arabs, there were important Armenian contingents in it.
When we next hear of Rustam, he has taken the part of Yazdgard III (who had been recently crowned) who had captured Ctesiphon and installed himself as regent. He was assisted in his rule by his brother Farrukhzad, who had been made the "darik-pat" (or chamberlain), and by another leader Zadhoe. It may be as Noldeke guesses that his support to the coronation of Yazdgard was simultaneous with his attack on the queen.
But while there was little so far to distinguish Rustam from other aristocratic claimants for power of the day in Iran, he and his brother honorably distinguished themselves by their single-minded devotion to the sovereign, whom they had raised to the throne, and to the task of defending Iran against foreign invaders. They went down fighting for their country and king to the last, harassed and handicapped though they were by intrigues at the capital as well as by the indifference of the majority of the Satraps to the cause of national defense. They have had their reward in the homage and admiration of Iranians ever since.
In the Iranian Epic, Rustam is endowed with a noble character and great Vigor; and he and his brother are held up to admiration as sole champions of Iran and of Yazdgard. Their unfailing loyalty and energy are contrasted with the treachery or feebleness of other Iranian spahbads. Nor have later historians failed to do justice to Rustam. Christensen describes him "as a man endowed with extraordinary energy, a good administrator and a fine general”. One might also quote the appreciation of Sir W. Muir: In Rustam “we may discern the lineaments of a prince brave in the field, but proud and over-weening. His energy was soon felt. The nobles rallied round him”.
Though Persia was destined to go down before the invaders from Arabia, fortune favored Rustam with at least one resounding victory, namely, that at “the battle of the Bridge”. He successfully recovered the delta from the Arabs and sent forward against the Arab commander Abu 'Ubaid the one Persian general in whom his troops had confidence, namely, Bahman Dhu-l-Hajib, With this latter was joined another general Jalenus, who had fled before the enemy before and who was now warned that the penalty of any further retreat would be death. Indeed, though Rustam was not himself present at the victory of al-Jisr (or the Bridge), yet that success was so closely associated with his name that such a great historian as Baladhuri names him as the victor. Relying therefore on such high authority, we may assert at least that the last victory of ancient Iran was won under the auspices of Rustam.
Bahman conducted the campaign with bravery as well as caution and allowed the Arab general Abu Ubaid to cross and place the river Euphrates behind him. When, therefore the Arab army emerged on the battlefield on the other side of the river, it found no room for maneuvering: very soon it was driven back on the river and hemmed in by a charge of elephants, while its general was trampled to death by the White Elephant. Indeed, only the skill of Mothanna, the lieutenant of Abu 'Ubaid, saved even a remnant of three thousand men. As it was, had Bahman been able at this juncture to pursue Mothanna, the Arab forces would have been entirely destroyed. But, at that time, Firuzan, the leader of the party of Persians proper; threatened the position of Rustam at the capital and thus the finest opportunity that Persia ever had in this war was irretrievably lost. As Sir W. Muir well observes, the one thing certain as regards the internal history of Persia at this great crisis of the Empire was that "the nobles sacrificed the empire to intrigue and jealousies". But, in spite of all this, Rustam had certainly finished one campaign against the Arabs with a decisive victory, a thing that had not been possible even for the Emperor Heraclius with all his prestige as a military genius and with the undivided resources of the Byzantine Empire at his disposal.
The Caliph Umar met this great reverse with his usual courage and firmness; but even so, as Baladhuri observes, "for one year after the calamity, that befell Abu Ubaid and Salit, Umar refrained from the mention of Iran. Meanwhile, however, Mothanna had gathered round his banner tribes of the frontier including even Christian tribes like the Beni Namr. He then advanced against the Persian general Mehran, who had reoccupied Hira. The battle took place at Boweib; and this time, experience induced Arabs to remain on the defensive and allow the Persians to cross the river and take the risk of an offensive. The Persians were defeated in the fight though the issue remained doubtful for some time.
The Arabs reaped the fruits of their victory by the occupation of Mesopotama and the Delta, while raids were being constantly made in other Persian territories to obtain supplies and to strike terror. Moreover the Caliph Umar was encouraged by the success to resume the invasion of Persia on a larger scale; and he gave the leadership to Sad ibn-abi Waqqas, who had the distinction of having been a Companion of the Prophet. Mothanna was superseded partly because he "was a mere Bedouin chief", and partly because he never really recovered from the wounds which he had received at the battle of al-Jisr, wounds which shortly after proved fatal. But before his death, he performed a great service to the Arab cause by advising Sad to meet the enemy bettveen Qadisiyyah and Udhaib. "Fight there the enemy," said the dying Mothanna, "for ye will be the victors; and even if worsted, ye will still have the friendly and familiar desert wastes behind. There the Persians cannot enter; and from thence ye will again return to the attack." The army of Sad was swollen by the new levy en masse ordered by the Caliph; and it contained "no fewer than 1,400 Companions, and ninety-nine, who had fought at Bedr". As to the total forces at the disposal of Sad accounts vary. Some put it about 30,000 men, taking Mothanna 's command at eight thousand, a similar number which Sad himself had brought up, and the Syrian levies as well as the new levies from Yemen and the South. He wisely followed the advice of the Caliph to practice patience and vigilance. He had chosen his battlefield well, his right resting on a great swamp and his rear and the other flank on the great Trench of Shapur, the fort of Qodeis and the desert.
The advance in person of Rustam who was now virtually the regent of Iran, though hampered by his rival Firuzan, could only meet such a great danger. His effort was worthy of his high position and energetic character. He retook much lost territory, advanced on Hira, reconquered it and rebuked the inhabitants for falling away from the old Empire. He is supposed to have “crossed the Euphrates below Babylon, encamped for a time near the ruined pile of Birs Namrud” and, passing by Najaf, faced the Arab army. As regards the size of the army which he commanded, we have widely different accounts. Some accounts put it as high as 200,000 men; others estimate it at 120,000 men. Of these latter 40,000 men are supposed to have formed the vanguard under Jalenus, 60,000 were in the main body under Rustam. But as a high authority has put it, "it is all guess-work".
Another account puts the Arab army at only five to six thousand; according to this view, the numerical superiority of the Arabs could not have been considerable. This last account very probably errs on the side of paucity. One element of Rustam's army deserves special notice. It consisted of a battalion of four thousand men from Dailain and was called "Jund-i Shahanshah", a sort of Imperial Guard. It would appear however that the solidarity of this northern race with the other races of old Iran was imperfect; for, on the death of Rustam, their contingent made terms with the Arab invaders, accepted Islam and received stipends from the former.
One thing is obvious that while the prudence and foresight of Umar placed the maximum possible number of Arab troops at the disposal of Sad, Rustam did not dispose of anything like the full military resources of the Persian monarchy. Not only individual nobles, but the Queen-mother herself, kept back very large bodies of troops, which, had they been joined to Rustam's army, would have decisively turned the tide of battle. This is obvious from the fact that very shortly after the battle of Qadisiyyah, another Persian noble, Nakhvargan, sallied from the capital to fight the Arabs on his own account.
Similarly, when the Arabs marched on the capital, the Queen despatched a third army against them which fought with them valiantly at the battle of Bahurashir being commanded by a veteran general designated as the “Lion of Chosroes.” Finally, soon after the fall of Medain, a fourth Persian army fought with the Arabs at Jalula. Baladhuri informs us that “the Persians were on this occasion led by Khurrahzad, a brother of Rustam. The fight that ensued was the fiercest they ever had, in which arrows and lances were used until broken to pieces, and swords were applied until they were bent”. As another authority puts it, the severity of this fourth battle "was not surpassed by the Night of Clangor at Qadisiyyah, excepting that it was shorter". But while the bravery of the Persian forces was undoubted, it is obvious that these masses were frittered away in successive engagements.
It remains to be added that quite a large contingent of Armenians accompanied Rustam to the battle-field. This was to be expected, since Rustam was the "ishkan" or prince of Azarbaijan. On this point Caetani, Dulaurier and Patkanian have collected much valuable information from old Armenian chronicles. We learn from these sources that Varaz-Grigor (Gregorio), prince of Alowan in Armenia, sent his forces under his brave son (named Jewansher) to join the Persian army at Ctesiphon. The chronicles tell us that Rustam "had hardly seen the young Armenian chief when he felt a great sympathy for him and treated him as a brother or a son". This narrative is important as showing prince Rustam’s kind and sympathetic manner of treating his subordinates. And here we might refer to one Bahman Hajib, who was the right-hand man of Rustam in thecampaign and who commanded the confidence of the troops as no other officer in the Persian army did. He was obviously a “fecht-general”, for we find him fighting and meeting a hero's death in the front lines of battle; and he was the first of the Iranian generals to fall on the field of honor.
Both Rustam and Sa’d marched towards the great encounter with suitable caution. The former is alleged to have taken four months to march from Medina to Qadisiyyah; and similarly, the latter left Medina in the spring while the battle was fought in November of the same year. Rustam, as the defeated party, has, however, received a greater share of blame. But both generals had no doubt great pre-occupations to detain them. Sa'd was constantly receiving reinforcements and required time to incorporate them into his army. Rustam had to reconquer and reorganize much territory as his base of operations, while he was certainly in no mood to respond to the impatience of the Persian court, or to the intrigues of his enemies at the court, who would have liked him to stake the fate of the Empire on a single battle fought at the earliest opportunity.
A word might be said about “the desponding dreams and auguries” of Rustam. No portents were required from supernatural quarters to inform that commander of the seriousness of his situation. The constant intrigues against him at the Persian court, which at once denied him the forces which he had a right to expect, and which put pressure on him to hasten the decisive struggle, were by themselves the worst omens. He was no doubt also well posted about the contemporary successes of the Arabs in Syria where they had won the battles of Wacusa and Fihl and were taking Damascus. He could not be ignorant that each of these successes made more and larger reinforcements available for the invaders of Persia. Moreover, for years the decline of the Persian monarchy had been obvious; thus the patriotic heart of the Persian general might well have been oppressed by this accumulation of unfavorable circumstances and he might well have seen corresponding portents in the heavens, with the help of the then fashionable science of astrology. But it might also be that Rustam resorted to these divinations in order to check the precipitous haste with which the court at Ctesiphon was bringing on a battle. Indeed one anecdote preserved for us by Tabari indicates that Rustam himself utilized either the skill or the dishonesty of the astrologers of the royal court at Ctesiphon for his own purposes. Thus, the services of the astrologer-royal, of one of his assistants and of an Indian astrologer of the name of Zurna were employed by Rustam himself to obtain his commission to march against the Arabs.
All authorities agree that before the final struggle in the field, there were interviews between Arab envoys and Rustam as well as with the king of Iran. On this subject, too, there is a diversity of accounts. One of the envoys sent by Sa’d to Rustam was al-Mughirah; and Baladhuri informs us that the latter “betook himself towards Rustam's throne, in order to sit by him, but was not allowed to do so by the Persian cavalry guard”. In the course of the interview, Rustam used both diplomacy and a show of superior force, as was indeed his true policy. That procedure is also indicated in the Shah-Nameh.