I just recently re-read the books. Looking at the map in FLF, makes me wonder a bit about the events of CuF. Did Jim just forget about Forcia? Tavi mentioned that the Canim sacked both Parcia and Rhodes, yet Forcia is closer to the Canim. Furthermore, two of Kalare's legions held the Blackhills to prevent a response from Parcia and the eastern legions. Forcia was in an ideal position behind all of Kalare's legions. They could of easily went on the offensive and taken the city in both CuF and CaF.
First off, congrats on a major resurrection of a zombie thread (almost 2 years!).
As to the heart of your question, in that instance Tavi was speaking historically. They had sacked those cities int he past, but during the events of the books, the incursion was held in the Vale north of Kalare, thanks mostly to a certain young upstart tactical virtuoso that shall remain nameless.
That being said, you are correct in that Forcia goes unmentioned in the various tactical discussions during the initial rebellion. It isnt until PrF when the legions of Forcia are mentioned, and in that case they are being largely dismissed as unlikely to be of any aid to the wider effort. If I had to find an in-world reason for it, Id say it is likely that the bulk of the Forcian leadership was lost during the mass coordinated assassination during the Night of the Red Stars at the start of the rebellion during CuF. By the time it is mentioned in PrC and FLF it is already under siege by the Vord, which makes sense as it is the region where the Vord were amassing their strength prior to the overt actions seen in those last two books.
