So, how long before "Test of Fire" did "Discovery" occurr?
Discovery occurred at the beginning of Roman expansion, about 60 to 65 Earth standard years before Time of Fire begins. So a lot of folks from then are getting up there in years. Even with the Telomerase anti-aging formula.
In that time they have met the Medians, fought them twice, the Atheri, an Avian species and found another connection to US Space. They also know about the Denevans, and have had some dealing with them through the Atheri, but did not know they had a connection to Denevan space. And that is the dangerous hole in their flanks.
Cheers, ??rgr?mr