When I see Mon Mothma and Admiral Ackbar together in Return of the Jedi, it seems to me like they have known each other for years. Yet, I have not seen Mon Mothma and Gial Ackbar together in any of Prequel movies or series. I have done numerous searches, and I haven't found any material that shows when these two meet for the first time.
At what point in the Star Wars timeline do Mon Mothma and Gial Ackbar meet for the first time?
According to The Official Star Wars Fact File #3, Ackbar escaped from Imperial captivity somewhere around 5-6BBY, returning to Mon Calamari and fomenting a rebellion against the Empire. He was promoted to Fleet Admiral by Mon Mothma some time around 4BBY. This is the first time that we have proof-positive of them meeting, although he was a Rebellion commander for at least a year prior to this and could easily have met her during this period.
...but secretly learnt all he could about his tormentors; studying their military doctrines and tactics, biding his time until he could escape and turn his knowledge against them.
Ackbar's opportunity came when, on a trip accompanying Tarkin to his rendezvous with the first Death Star, the governor's vessel was attacked by Rebel forces. Ackbar duly escaped, and pledging to join the Rebellion, he returned to Mon Calamari to enlist the support of his people.
ASSET TO THE ALLIANCE: Among the Mon Calamari's substantial contributions to the Alliance were their giant MC 80 star cruisers, some of the only Rebel ships capable of standing toe-to-toe with the Empire's Star Destroyers. Ackbar, now an Alliance Commander, also collaborated on the top-secret Project Shantipole. The goal was to develop a fighter capable of tackling much larger enemy capital ships. The result was the B-wing, the most heavily armed Rebel starfighter. Upon delivery of the B-wing prototypes, Ackbar was promoted to Admiral by Alliance leader Mon Mothma.