How hard was the Reach invasion for the Covenant?

Before I start, I don’t know if this belongs in Reach or the Halo Universe thread… but y’know. Whatever.

Did the Covenant realize the difficulty of invading Reach? Is that why they sent ‘the whole damn Covenant fleet!’, or was it just another planet to grab and strip to the core for relics? I thought that, even though the Reach campaign only shows the battle of six Spartans, and not the worldwide battle. That and the campaign is not entirely linear, it skips the boring parts and shows only the important stuff. So, how long did it take the Covenant to defeat the UNSC on Reach? And did they also suffer substantial losses? I like to think that Reach truly was the ultimate battle. Not the last, but the most intense and biggest, where the heavy blows were truly dealt. The typical ‘You’re going to send us to hell? -Yoink- it, I’m gonna drag you down there with me!’

Was easy enough as they steamrolled the planet

Ease depends on how many troops casualties and ships they lost, and that depends on which story you want to go with. The book or the game.