The multiple statements in Diodoros? Just this one 17 5 3
3 As our narrative is now to treat of the kingdom of the Persians, we must go back a little to pick up the thread.14 While Philip was still king, Ochus15 ruled the Persians and oppressed his subjects cruelly and harshly. Since his savage disposition made him hated, the chiliarch Bagoas, a eunuch in physical fact but a militant rogue in disposition, killed him by poison administered by a certain physician and placed upon the throne the youngest of his sons, Arses. 4 He similarly made away with the brothers of the new king, who were barely of age, in order that the young man might be isolated and tractable to his control. But the young king let it be known that he was offended at Bagoas's previous outrageous behaviour and was prepared to punish the author of these crimes, so Bagoas anticipated his intentions and killed Arses and his children also while he was still in the third year of his reign.16 5 The royal house was thus extinguished, and there was no one in the direct line of descent to claim the throne. Instead Bagoas selected a certain Dareius, a member of the court circle, and secured the throne for him. He was the son of Arsanes, and grandson of that Ostanes who was a brother of Artaxerxes, who had been king.17 6 As to Bagoas, an odd thing happened to him and one to point a moral. Pursuing his habitual savagery he attempted to remove Dareius by poison. The plan leaked out, however, and the king, calling upon Bagoas, as it were, to drink to him a toast and handing him his own cup compelled him to take his own medicine.
Aelian 6 8
They say that Artaxerxes surnamed Ochus, being by Bagoas the Eunuch, who was an Aegyptian, slain and cut into pieces was thrown to cats, and some other buried in his stead was laid in the Regal Momuments. The sacrileges which are reported of Ochus are many, especially those committed in Aegypt. Neither was Bagoas satisfied with killing Ochus, but he also made hilts for swords of the bones of his thighs: thereby signifying his bloudy disposition. He hated him, because when he came into Aegypt he slew Apis as Cambyses had done before.
Strabo 15 3 24
Cyrus was succeeded by his son Cambyses, who was deposed by the Magi. The Magi were slain by the Seven Persians, who then gave over the empire to Dareius, the son of Hystaspes. And then the successors of Dareius came to an end with Arses. Arses was slain by Bagoüs the eunuch, who set up as king another Dareius, who was not of the royal family. Him Alexander deposed, and reigned himself for ten or eleven years.
Plutarch De fort Alex 5
The eunuch Bagoas took up the kingship of Persia and bestowed it upon Oarses and Darius.
Curtius 5 3 12
Even Darius did not inherit his rule of the Persians: he owed his succession to the throne of Cyrus to the benefaction of the eunuch Bagoas.
The question is are these secondary sources using independent primary ones or are they ultimately dependent on just one. That Diodoros Book XVII is based on Kleitarchos is not exactly a given but it is certain that he used him, Strabo quotes him (V 2, VII 2, XV 1) as does Curtius and Plutarch had used him too nor do their perfunctory notes that Bagoas arranged the succession require them to have read any more than the retrospective notice preserved in the Diodoros quote. Aelian is another matter as his farrago is too detailed to have come from an Alexander History so we should look for a Persika one of which was written by the father of Kleitarchos one Dinon whom Aelian quotes twice (VH VII 1, Nat Animal. XVII 10). It is certainly possible that the fact of Bagoas’ emasculation stems from this one source.
Against which we have the connected and detailed narrative of Diodoros XVI 47ff, where no mention is made of his enuchhood nor his alleged Egyptian ancestry which IMHO militates against the accuracy of Aelian’s sensationalist source.
47 Then on the next day, as the king divided the Greek army into three contingents, each contingent had a Greek general, and stationed along beside him a Persian officer, a man preferred above the others for valour and loyalty. 2 Now the forward position was held by the Boeotians, who had as general the Theban Lacrates and as Persian officer Rhosaces. The latter was a descendant of one of the seven Persians who deposed the Magi;19 he was satrap of Ionia and Lydia, and he was accompanied by a large force of cavalry and no small body of infantry composed of barbarians. 3 Next in line was the Argive contingent of which Nicostratus was general and with him as Persian colleague Aristazanes. The latter was an usher20 of the King and the most faithful of his friends after Bagoas; and assigned to him were five thousand élite soldiers and eighty triremes. 4 Of the third contingent Mentor was general, he who had betrayed Sidon, having the mercenaries that were formerly under his command; and associated with him on the expedition was Bagoas, whom the King trusted most, a man exceptionally daring and impatient of propriety; and he had the King's Greeks and an ample force of barbarians and not a few ships. 5 The King himself with the remainder of the army held himself in reserve for the whole operation.21 Such being the distribution of the army on the Persian side, the king of the Egyptians, Nectanebôs, was dismayed neither by the multitude of the enemy nor by the general disposition of the Persian forces, though his numbers were far inferior. 6 In fact he had twenty thousand Greek mercenaries, about the same number of Libyans, and sixty thousand Egyptians of the caste known amongst them as "The Warriors", and besides these an incredible number of river-boats suited for battles and engagements on the Nile. 7 The bank of the river facing Arabia had been strongly fortified by him, being a region crowded with towns and, besides, all intersected by walls and ditches. Although he had ready also all the other preparations which were adequate for the war, yet because of his own poor judgement he met with complete disaster.
48 The reason for his defeat was chiefly his lack of experience as a general and the fact that the Persians had been defeated by him in the previous expedition. 2 For he had then had as his generals men who were distinguished and superior both in valour and in sagacity in the art of war, Diophantus22 the Athenian and Lamius the Spartan, and it was because of them that he had been victorious in all respects. At this time, however, since he supposed that he himself was a competent general, he would not share the command with anyone and so, because of his inexperience, was unable to execute any of the moves that would have been useful in this war. 3 Now when he had provided the towns here and there with considerable garrisons, he maintained a strict guard there, and having in his own command thirty thousand Egyptians, five thousand Greeks, and half the Libyans, he held them in reserve to defend the most exposed approaches. Such being the disposition of the forces on both sides, Nicostratus, the general of the Argives, having as guides Egyptians whose children and wives were held as hostages by the Persians, sailed by with his fleet through a canal into a hidden district and, disembarking his men and fortifying a site for a camp, encamped there. 4 The mercenaries of the Egyptians who were keeping a strict guard in the neighbourhood, observing the presence of the enemy, straightway made a sally in number not less than seven thousand. 5 Cleinius the Coan, their commander, drew up his force in line of battle. And when those who had sailed in were drawn up opposite, a sharp battle ensued in the course of which the Greeks serving with the Persians, fighting brilliantly, slew the general Cleinius and cut down more than five thousand of the rest of the soldiers. 6 Nectanebôs the Egyptian king, on hearing of the loss of his men, was terror-stricken, thinking that the rest of the Persian army also would easily cross the river. 7 Assuming that the enemy with their entire army would come to the very gates of Memphis, he decided first and foremost to take precautionary measures to protect the city. Accordingly he returned to Memphis with the army he had retained and began to prepare for this siege.
49 Lacrates the Theban, who was in command of the first contingent, hastened to begin the siege of Pelusium. First he diverted the stream of the canal to other directions, then when the channel had become dry he filled it with earth and brought siege engines against the city. When a large portion of the walls fell, the garrison in Pelusium quickly built others to oppose the advance and reared huge towers of wood. 2 The battle for the walls continued for several days running and at first the Greeks in Pelusium vigorously warded off the besiegers; but when they learned of the king's withdrawal to Memphis they were so terror-stricken that they sent envoys to arrange for a settlement. 3 Since Lacrates gave them pledges backed by oaths to the effect that if they surrendered Pelusium they would all be conveyed back to Greece with whatever they could carry on their backs, they delivered over the citadel. 4 After this Artaxerxes dispatched Bagoas with barbarian soldiers to take over Pelusium, and the soldiers, arriving at this place as the Greeks were issuing forth, seized upon many of the articles they were carrying out. 5 The victims of this injustice in their anger called loudly upon the gods who were guardians of their oaths, whereupon Lacrates became incensed, put the barbarians to flight, slaying a number of them, thus standing by the Greeks, the sufferers from the broken pledges. 6 But when Bagoas fled to the King and brought accusation against Lacrates, Artaxerxes decided that Bagoas' contingent had met with their just deserts and put to death the Persians who were responsible for the robbery. So it was in this fashion that Pelusium was delivered over to the Persians.
7 Mentor, who was in command of the third contingent, captured Bubastus and many other cities and made them subject to the King by a single strategic device. For since all the cities were garrisoned by two peoples, Greeks and Egyptians, Mentor passed the word around to the soldiers that King Artaxerxes had decided to treat magnanimously those who voluntarily surrendered their cities, but to mete out the same penalty to those who were overcome by force as he had imposed on the people of Sidon; and he instructed those who guarded the gates to give free passage to any who wished to desert from the other side. 8 Accordingly, since the captured Egyptians were leaving the barracks without hindrance, the aforementioned word was quickly scattered amongst all the cities of Egypt. Immediately, therefore, the mercenaries were everywhere at variance with the natives and the cities were filled with strife; for each side was privately endeavouring to surrender its posts and nursing private hopes of gain in exchange for this favour; and this is what actually happened in the case of the city of Bubastus first.
50 When, namely, the forces of Mentor and Bagoas were encamped near Bubastus, the Egyptians, without the knowledge of the Greeks, sent an envoy to Bagoas offering to deliver the city if he would consent to their safety. 2 The Greeks, having knowledge of the mission, overtook the envoy and by dire threats extracted the truth, whereat they were much enraged and attacked the Egyptians, slew some, wounded others, and herded the rest into a quarter of the city. 3 The discomfited men, having notified Bagoas of what had taken place, asked him to come with all speed and receive the city from themselves. But the Greeks had been privately treating with Mentor, who gave them secret encouragement, as soon as Bagoas should enter Bubastus, to attack the barbarians. 4 Later on, when Bagoas with the Persians was entering the city without the sanction of the Greeks and a portion of his men had got inside, the Greeks suddenly closed the gates and attacked those who were inside the walls, and, having slain all the men, took Bagoas himself prisoner. 5 The latter, seeing that his hopes of safety lay in Mentor, besought him to spare his life and promised in future to do nothing without his advice. 6 Mentor, who now prevailed upon the Greeks to set Bagoas free and to arrange the surrender through himself, won credit himself for his success, but, having become responsible for Bagoas' life, he made an agreement with him for common action, and after an exchange of pledges on this matter kept the agreement faithfully till the end of his life. 7 The result of this was that these two by their co�operation in the service of the King attained later on to the greatest power of all the friends and relatives at Artaxerxes' court. In fact Mentor, having been appointed to the chief command in the coastal districts of Asia, performed great services to the King in gathering mercenaries from Greece and sending them to Artaxerxes, and in the course of his activities administering all his duties courageously and loyally. 8 As for Bagoas, after he had administered all the King's affairs in the upper satrapies,23 he rose to such power because of his partnership with Mentor that he was master of the kingdom, and Artaxerxes did nothing without his advice. And after Artaxerxes' death he designated in every case the successor to the throne and enjoyed all the functions of kingship save the title. But of these matters we shall record the details in their proper chronological sequence.
51 At the time under consideration, after the surrender of Bubastus, the remaining cities, terror-stricken, were delivered to the Persians by capitulation. But King Nectanebôs, while still tarrying in Memphis and perceiving the trend of the cities toward betrayal, did not dare risk battles for his dominion. So giving up hope of his kingship and taking with him the greater part of his possessions, he fled into Aethiopia. 2 Artaxerxes, after taking over all Egypt and demolishing the walls of the most important cities, by plundering the shrines gathered a vast quantity of silver and gold, and he carried off the inscribed records from the ancient temples, which later on Bagoas returned to the Egyptian priests on the payment of huge sums by way of ransom. 3 Then when he had rewarded the Greeks who had accompanied him on the campaign with lavish gifts, each according to his deserts, he dismissed them to their native lands; and, having installed Pherendates as satrap of Egypt, he returned with his army to Babylon, bearing many possessions and spoils and having won great renown by his successes.
I think forum members can draw their own conclusions about the weight of evidence.
When you think about, it free-choice is the only possible option.