Why can't I invade enemy planet?

[xxHanasaku]

I'm at war with an alien empire and I have eliminated all resources operations in a system and taken out the planet's star base. I have bombed fortifications to rubble, brought in the ground pounders and tried to assault the planet.

The game won't let me land the troops. I think the reason is that this is a desert planet and I don't have the ability to colonize desert planets yet (we're working on it). Can someone please confirm or provide the correct reason? If my reasoning is correct, it seems like the message could have been worded better. Otherwise, great game.

[Valentine Michael Smith]

you shouldn't need colonization tech to invade. Not enough info to help you anymore than that tho. Did you build armies and send the transport ships to invade?

[Z-hog]

force use you must luke!

[kbmodigity]

Is another empire at war with them and did they land troops first? If they took it over before you and you arent at war with them you cant land troops unless they take thiers off.