Diadochi

The Diadochi (/daɪˈædəkaɪ/; plural of Latin Diadochus, from Greek: Διάδοχοι, Diádokhoi, "successors") were the rival generals, families and friends of Alexander the Great who fought for control over his empire after his death in 323 BC. The Wars of the Diadochi mark the beginning of the Hellenistic period.

An army on campaign changes its leadership at any level frequently for replacement of casualties and distribution of talent to the current operations. The institution of the Hetairoi gave the Macedonian army a flexible capability in this regard. There were no fixed ranks of Hetairoi, except as the term meant a special unit of cavalry. The Hetairoi were simply a fixed pool of de facto general officers, without any or with changing de jure rank, whom Alexander could assign where needed. They were typically from the nobility, many related to Alexander. A parallel flexible structure in the Persian army facilitated combined units.

Staff meetings to adjust command structure were nearly a daily event in Alexander's army. They created an ongoing expectation among the Hetairoi of receiving an important and powerful command, if only for a short term. At the moment of Alexander's death, all possibilities were suddenly suspended. The Hetairoi vanished with Alexander, to be replaced instantaneously by the Diadochi, men who knew where they had stood, but not where they would stand now. As there had been no definite ranks or positions of Hetairoi, there were no ranks of Diadochi. They expected appointments, but without Alexander they would have to make their own.

For purposes of this presentation, the Diadochi are grouped by their rank and social standing at the time of Alexander's death. These were their initial positions as Diadochi. They are not necessarily significant or determinative of what happened next.

In Hellenistic times the title Diadoch was actually the lowest in a system of official rank titles. It was first used in the 19th century to denote the immediate successors of Alexander.

...
Wikipedia