Really, thats all we knew. The only additional specifics is in relation to the Clone War--not Mandolorians but "Imperial Shocktroopers." These were super-troopers of a distant origin, of which Boba Fett was a part of, who fought a war called the Clone War, which the Jedi were involved in, but were defeated by the Jedi.

Here's exactly from the novelisation: "[Boba Fett] was dressed in a weapon-covered, armored spacesuit, the kind worn by a group of evil warriors defeated by the Jedi Knights during the Clone Wars."

I don't care for the John Flynn story treatment. He's also the one to start the whole Obi-Wan = OB1 tripe. *Gasp!* He's a clone! I never liked the idea of cloning Jedi as a story element.