Multi-player campaign team mate?

[cubicleclown]

Hi, I'm interested in purchasing this game, but I have some questions first, and would appreciate any answers.

1) How many players (including ai) can there be in a multi-player campaign?
2) Can you be allies with another human player?
3) I've read some about people having frustrating multi-player game crashes and such, how big of a problem is this? Does it effect everyone, or just an unlucky few?

Thank you

[cubicleclown]

Think I'm gonna go with shogun 2 instead, sounds a lot better, definitely has co-op campaign, the ai has a higher review, and the game sounds more stable. Thanks for the answers!