User blog comment:Etindel/That did NOT just happen!/@comment-15843945-20130606194856/@comment-10385544-20130610175126

"Most notably though, he commanded Tyrion to marry Sansa. Why would he do that if he wasn't sure that Robb was going to fail. Surely trying to get him to marry someone like say, Asha Greyjoy would have been more rewarding. But no, Tywin had the Red Wedding all planned out for quite a while."

The Lannisters, and most everyone else in King's Landing, have been speaking about Rob Stark almost in the past tense for most of the season. It's almost as if it were a foregone conclusion that King Rob would be killed, and they were already planning the next moves to stay one step ahead of current events.

For Lord Tywin to marry Tyrion to marry Asha Greyjoy would serve the Lannisters far less than Tyrion marrying someone from the Iron Islands. The northern lands are far larger and worth far more than Iron Islands. Doing so would also leave the North open to conquest by someone else, like Lord Bolton's Bastard has already apparently done to most of it.

I think that you're spot on about all of it, except for House Lannister marrying with House Greyjoy. House Lannister could gain more by going elsewhere, like laying the Foundation to a Lannister claim to the North while everyone is looking the other way.