[Patrikc]

Originally Posted by Mzyxptlk

I had it the wrong way around. When you're in a tag, you can only defend people in that tag (with ETA advantage), and all the tags it's napped with (without ETA advantage). When you're not in a tag, you can defend everybody (without ETA advantage). The point stands, though.

You had it correct the first time around. You need to be either in the alliance or napped to the alliance you want to defend. Planets without a tag can only defend in galaxy / others without a tag.