To shed a little more time to the ISC, in SFC timeframes. From memory, dates may be a little off...
FIrst Contact 2269, saw Gorn / Romulan battle, of which there were no survivors.
Ambassadors sent to Gorn / Romulus. ISC thought people barbaric (due to constant fighting)
Learned of rest of galaxy, sent ambassadors to most of them. Decided that further west they went (closer to Mirak / Lyran lunchhalls...) the galaxy was more and more barbaric... ISC quickly secures their Romulan and Gorn borders, and begins "agressive" border expansion by claiming unoccupied systems. A single ship was enough to "occupy" the system and cause the ISC to ignore it. If the ship ever left the system however, the ISC would "liberate" it.
2286, most races slowing down (wartime economy hurting major powers), power construction program has ISC fleet up to the size of any 3 races added together. "Pacification effort" begins. The pacification effort was a plan to occupy all the neutral zones in an effort to prohibit empires from expanding militaristically. In a short time, they were occupying all neutral zones from their border out to the Lyran / Mirak zone...
2289, Andromedans invade. Since the ISC fleet was dispersed all over the galaxy, 2/3rds of it was destroyed in the initial attacks, the same attacks that claimed the LDR, and saw a large portion of the galaxy conquered. The ISC regroups and joins Operation Unity, ending the Andromedan threat in 2302. Following that operation, with a fleet about the same size as anyone else, the ISC starts to take on a more "militaristic" outlook, beginning to fight and war like the rest of the galaxy...