Quote Originally Posted by seleucid empire View Post
well, really it was only Rome that had full time professional troops
Actually, the Roman legions that defeated the Diadochi were still the conscript levy. That said, those particular levies consisted mainly of veterans from the second Punic War, so they would have had more experience than the professionals they opposed.

I am not sure I know how Diadochi recruitment worked (and no doubt it varied depending on time and place), but IIRC foot companions were settlers from "military colonies": in return for the right to settle they were obliged to serve the Diadochi kings. A pike-formation does require a great deal of drill to function effectively, so no doubt they had received at least some training.