Is it possible to bypass enemy space defenses in Star Wars: Empire at War?

While playing the Empire campaign in Star Wars: Empire at War, I've noticed that the Rebels' fleets sometimes ignore my space defenses if I only have a space station and no ships.

More specifically, I remember the Rebels were able to move some ground units to Endor, and attack my ground forces there while ignoring my space station. When playing the Rebel campaign, I was able to do the same thing to Imperial-controlled Mon Calamari.

However, I was unable to replicate this behavior for other planets, so I think it might have something to do with whether the local population helps you (both Ewoks and the locals on Mon Calamari help the Rebels).

Could anyone clarify how this works?

Solution 1:

This is a special ability the Rebel faction has. You can't stop them from bypassing your space fleet. It's called a "raid fleet". It's limited in size (maximum of four, non-hero units), so they can't bring a ton of units, but they do get to go straight to the planet's surface. The Rebel single-player campaign has a pretty good introduction to their use.

As far as I know, the only defense you can mount, really, is to make sure that every important planet has sufficient forces garrisoned to defend. You can't stop them from taking you by surprise, but you can make sure your defenses are good.