This note contains spoilers for the book.

A compendium containing Falkenberg's Legion (1990), Prince of Mercenaries (1989), Go Tell the Spartans (1991) (with S. M. Stirling) and Prince of Sparta (1993) (with S. M. Stirling). I'm reading it courtesy of one of the Baen Books free releases (I'm not sure at this point if it was the online free library or one of the CDs distributed in various books).

Lots of stuff (1100 pages in the hardcover) in the declining years of the Codominium, including quite a lot with the mercenary outfit run by John Christian Falkenberg III, and with Prince Lysander of Sparta working with them. This is the back-story of The Mote in God's Eye (#2), showing some of the seeds that the future empire condensed out of, and establishing some of the major character lines (governor Blaine is probably an ancestor of Rod's, and there's a reference to Crucis Court as well).

It does indeed, as I was starting to expect, follow through to the exact moment where Lysander is proclaimed emperor (in Latin, yet).

It strikes me that SF writers have been discussing the fall of civilization and the hopeless state of education since before Heinlein, and yet people I know with highschool students say their kids are learning advanced stuff they never saw in school.