This is kind of a last-ditch effort piece of advice. Say that you have all the defenses on a planet, and the empire shows up, kicks the shit out of your fleet and then begins destroying your gencores. At this point it's obvious their going to take the planet, so don't give em much of a planet! When all of this starts happening start destroying the mines, refineries, and construction/ship/training yards on the planet. That way the empire has to rebuild, which takes time and energy, and they don't get anything out of the planet right away. But yeah, I'd say for defending a planet, what I do a lot of the time is build some corvettes, like 8 or 9, and have them engage the carracks, along with two or three drednoughts. Then I have the gunships and the fighters target the enemy fighters, and once they are all down you can attack the larger ships like the stardestroyers with the x-wings and y-wings (which is a pain in the ass for the SD). Its not a great strategy but it works from time to time. Be sure to use the top strategy idea though, it pisses the shit out of other players...