Digby: Why oh Y

Matt Yglesias took up the "why did we invade Iraq?" meme on Tuesday and others have followed. Matt says:.

... there's a difference between observing that the United States went into war without a plan -- without a realistic assessment of what we could accomplish, how it could be accomplished, and whether the costs of such a course of action would outweigh the benefits -- and the news that our main ally in the conflict made that observation long before the war happened. Yet the Brits joined up anyway. Why?