"...They now occupy an area of space of unknown size, with an unknown number of Gbaba inhabited plants in it, and unknown resources available...."
This has been said several times, so I will not blame anyone in particular for saying it.
On one hand, during the Federation counterattack, the Federation captured several Gbaba planets, so there should be no doubt as to whether or not the Gbaba are currently sentient, even if they all committed suicide when the Federation Army landed. Captured public libraries or spaceliner schedules should contain much information as to other planets.
On the other hand, assuming that the Federation was run by moderately competent people, long-range reconnaissance ships should have been sent into Gbaba space, never entering a solar system where they would be detected (note the start of the first chapter of the first book, in which the Gbaba are not seen until they appear at the edge of the system), but mapping the extent of Gbaba space from, e.g., radio emissions.
