How hard is it to conquer an abandoned planet

[plug]

I just lost 4 billion marines doing it

And it didn't even scratch the surface !

I have no experience on the planet thingy, can someone please give me some pointers?

[Spayed]

it depends how big the planet is and what the combat bonus is.

its best if you know these things before you start attacking.

[Saturn 7]

I suggest you scan planets before you even consider attacking them, combat bonus, shields, colonist numbers and capacity are a major factor when it comes to its defence capabilities.