The infantry marched outside Babylon’s walls, into the stronghold of the cavalry, to enact the solemn rite of lustration. From the opposite side of the field, the cavalry came forward in full armor, led by a wedge of war elephants. This exotic weapon had terrified the Macedonians when they first encountered it in India, but they had quickly learned how to check it, then mastered it themselves. Elephants had since become an accustomed sight in Macedonian camps, but to see them marching in a lustral procession was strange and, no doubt, disquieting.

As the distance between ranks closed, Perdiccas sprang his trap. He sent King Philip over to the infantrymen with a prepared speech demanding surrender of the leading mutineers—the very men who had put him on the throne and given him his name—and to threaten a devastating cavalry charge if they refused. Meleager had been double-crossed but could do nothing about it. His thirty staunchest supporters were handed over, bound, and, as the assembled infantry looked on, cast under the feet of the elephants and trampled to death. With a single macabre stroke, the army was purged of its most troublesome members. But Perdiccas’ duplicity was not without its costs. From this point on, the chiliarch became “suspected by all and full of suspicions,” says Photius, summarizing the view of Arrian in the lost Events After Alexander.

Meleager himself escaped the lustration, but a few days or perhaps a few hours later his own reckoning with Perdiccas arrived. When officers appeared accusing him of treachery, Meleager did not bother to defend himself. He fled to a nearby temple, trusting in the ancient taboo against harming those seeking sanctuary at altars of the gods. But such taboos were a luxury that could not be afforded in the current crisis. Perdiccas ordered his troops to enter the enclosure and drag Meleager away. King Philip, indifferent to or barely cognizant of his change of masters, signed the order for Meleager’s execution as compliantly as he had earlier signed a similar writ against Perdiccas.

•  •  •

Having literally stomped on the spirit of sedition in the army, Perdiccas plotted a second purge of a very different kind. We know almost nothing about this plot because only one ancient chronicler, Plutarch, mentions it, and only in a single, short, confusing paragraph. But there is no reason to doubt that it took place. In this case Perdiccas had an unusual collaborator, a woman unaccustomed to political murders: Alexander’s pregnant young widow, Rhoxane.

Rhoxane must have realized, during the days after Alexander’s death, that she had become presumptive queen mother. But she also knew that her lofty status was a fragile thing. Alexander’s two other widows, Stateira and Parysatis, were daughters of the two most recent Persian kings. Alexander had intended to beget children by them, children who, with both European and Asian royal blood, would be ideal rulers of the Perso-Macedonian empire. Now these two Persian princesses offered an opportunity for someone else, one of Alexander’s generals presumably, to sire sons who were royal at least on their mother’s side. In the new political landscape, with Europe and Asia forced together by Alexander’s titanic will, it was unclear whether such children could become candidates for the throne. A more confusing possibility was that one or both princesses were already pregnant by Alexander or would claim to be—a claim that would pose great perils for Rhoxane and her unborn child.

So Perdiccas and Rhoxane, acting together, resolved to murder at least one, more likely both, of the Persian princesses. A letter, tricked up to look as though it came from Alexander, was brought to Stateira. Since Perdiccas had control of Alexander’s signet ring, it is tempting to think he used it to seal the forged letter. Whatever Stateira read in that letter drew her to a spot where Rhoxane was waiting for her, and where Rhoxane had her killed, together with another woman, probably Parysatis. Then the bodies were secretly cast down a well and the well was filled in with earth. Rhoxane and Perdiccas meant no one to learn what had happened; they simply made the two women disappear. If not for a single sentence in Plutarch, derived from some unknown informant, the crime would have remained hushed up to this day.

There is a verb, phthanō, in ancient Greek that denotes the taking of preemptive action, especially where one harms an enemy to prevent that enemy from doing harm. When Alexander had a high-ranking officer named Philotas tried and executed, on thin evidence of collusion in an assassination plot, he named the city founded at the trial’s site Prophthasia, the place where he had gotten the jump on danger. Prophthasiahad always been the prerogative of Macedonian kings. The safety of the monarch justified the elimination even of anticipated threats. But the murder of the Persian princesses by Rhoxane and Perdiccas took this logic to a new extreme. Heirs to the throne had been rubbed out before, but killing women to prevent them from bearing heirs was unprecedented.

Once this logic of prophthasiawas invoked, it was hard to limit how it was applied. The violence it seemed to license would, in years to come, claim the lives of all the women who shared Alexander’s blood or who had shared his bed. Somehow one unlikely survivor would escape the carnage to help beget a new royal line.

In either July or September—our sources are divided on the chronology—Rhoxane gave birth to a boy. Never before or since, one imagines, was the gender of an infant anticipated so keenly by so many. Most were no doubt relieved, but none more so than Perdiccas. The settlement he had masterminded was secure. His plan for the future of the empire, which, like Alexander’s, called for a center of power at Babylon rather than in Europe, could go forward.

The baby was named for his father, as was inevitable given that his counterpart had been renamed after hisfather. A new Alexander was now acclaimed as king alongside a new Philip. History knows the pair as Alexander IV and Philip III (sometimes called Philip Arrhidaeus).

The time had come for Perdiccas to give new assignments to the Bodyguards, since it did not suit their training or temperament to attend a mental invalid or a suckling infant. Perdiccas needed to reward those who had stayed loyal during the infantry uprising and also get rivals off the scene. It was resolved that each Bodyguard, Perdiccas excepted, would leave Babylon and become a satrap, or provincial governor (the Persian name for the office had already been adopted into Greek, and as a result survives today in English). Such appointments conferred power and status, and were strategically important as well, for satraps controlled small armies that could cement the unity of the empire—or, if used for revolt, destroy it. It was essential that the heads of the provinces be reliable men, strong but not too strong, who would follow orders issued by Perdiccas in the name of the joint kings.

The division of these posts, however, posed a complex problem in diplomacy. Perdiccas could not risk offending his comrades by giving them too paltry a province or emboldening them with one too powerful. In the end he made errors on both sides of this delicate balance, errors that would soon threaten the survival of his regime.

The biggest question Perdiccas faced was how to accommodate Ptolemy, the second most powerful Bodyguard. Ptolemy clearly disliked him yet had supported him during the infantry insurrection. Ptolemy wanted Egypt. It was a gem of a province, wealthy beyond measure and friendly to the Macedonians, with borders that were easy to defend—all too easy, in Perdiccas’ eyes. Ptolemy could not be denied Egypt without risking a severe breach, but he also could not be allowed to use it as a base for mounting revolt. A diplomatic solution was found: Ptolemy got his wish but was also assigned an adjutant, Cleomenes of Naucratis, an unscrupulous Greek who was already serving in Egypt as finance minister. Cleomenes was clearly meant to watch Ptolemy on Perdiccas’ behalf and keep him from misbehaving.