My question has a minor spoiler in it, just FYI.

**** SPOILERS BELOW ****
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When you receive the offer in the middle of the campaign to switch sides, what missions do you get after that? Are they just the second half of the other side's missions? Or are they totally different because of your defection?

Thanks!

Kind of, but from mission 7 onwards you're at a severe disadvantage due to the lack of the Dwarf\Ogre Alliances and other bonuses.