I believe I either read it in the interest check or maybe in a Discord conversation that the Great War ended about 3-5 years prior to the start of the RP, if that's any help to you.  I think it's being kept somewhat ambiguous because the exact detail hasn't been necessary to the RP, but it has to be a certain number of years afterward to give a chance for the Academies to get up and running, but not long enough for there to be actual graduates.  The training could have started right away even while the Academies were under construction, and it takes four years to graduate, so closer to the 3 year mark might work best overall.

(not trying to supplant the GM or anything, just trying to provide info from what I remember seeing being said + adding some interpretation of the OOC details about how cadets are being picked for this assignment prior to there being any real graduates, hopefully to save some time for Nutts when he's more available to answer questions)

I don't have any info on number of characters, since this is the first time the question was raised; I'd be interested in knowing the answer to that, too.