The Andians not only had several very large and powerful fleets, they actually invaded and captured planets. Never seen that up to now. Is this just a quirk, or does this happen in anyone elses campaign's? It's refreshing to see, and made for a scramble to create fleets to counter them...and with a 366Pt. defense for a 7-ship fleet, I had to scramble quickly
Yes, minor races can occasionally develop into decent powers. I've undergone extensive modding efforts to make my minors tougher, but even in the unmodded game, it's still possible. Normally, it happens when the "minor race steals a major race's techs and wants to trade them for planets" event takes place, as this gives the minor a gigantic technological boost, particularly if it stole from the game's tech leader.
Surprise #2 came when I attacked them. Two of the remaining major races were allied with them. I didn't know it was possible to form an alliance with a minor race. This begs the question of...can a player form an alliance with a minor, and if so, how? I would assume you just keep opening the dialogue screen until the Alliance option appears, yes?
You ally with a minor race just like you do a major race. Nothing special about it, though it's usually not a good idea unless the minor can take care of itself, as you'll frequently be dragged into lots of wars.