Id never invaded a planet before, but i discovered one awhile back that was pretty juicy.
Get all set up with my off, def, and shields, ready to conquer full energy too. level 3 ship defending out of protection.
everything is looking perfect, start my attack bam bam bam, get the population below 10, disable his ship. But to my suprise, the invasion cost almost double the colonizing cost, and now im 200k credits short with not too much to vendor...
Scrap everything i could, including everything on my ship...only to have my invasion stopped because i vendored all my attack shields etc...

24 hours til i can try again. hopefully with less fail

ya you need higher attack then the planets defense to even have a fair chance of invading it