Hi, folks. Long time reader, first time poster, as they might say.

Anyhoo. I was rereading Roland's flashback to the battle (one of my favorite passages in the book and the whole series, for that matter), and something popped out at me again:

Quote Originally Posted by Stephen king
"Roland!" he cries. "We've been betrayed! We're outnumbered! Our backs are to the sea! We've got em right where we want em! Shall we charge?"

And Roland understands he is right. If their quest for the Dark Tower is really to end here on Jericho Hill -- betrayed by one of their own and then overwhelmed by this barbaric remnant of John Farson's army -- then let it end splendidly.
So... who was the traitor? It wasn't Alain or Jamie, unless Roland was doing some seriously selective remembering earlier in the flashback. Thomas Whitman is the only other gunslinger we know by name. Was it him? Why? Or was it Sheemie, inadvertantly causing disaster? Theories? Speculation?