In 1999, Marine Gen. Anthony Zinni commissioned Booz Allen Hamilton (a government contractor with a large gaming shop) to produce a wargame (titled Desert Crossing) to examine the issues that would surround US intervention in Iraq. The after-action report and some related documents were declassified late last year, and much of it is available through GWU's National Security Archive website. Prior to declassification, Gen. Zinni mentioned the game in several public contexts, and Tom Ricks included a brief description of the game in his book Fiasco.
There were a number of mentions of Desert Crossing in the press when the documents became publicly available, as well as some attention from the blogosphere. Many of these comments were directed specifically at the number of troops the game participants assumed would be necessary to occupy Iraq, in contrast to the number that were actually used four years later. But the game is much more interesting than a simple question of troop numbers, and the troop number issue is a bit of a red herring compared to the broad insights that emerged from the game. The game was run to identify problem areas for future consideration, which it did. Despite the fact that the scenario was largely directed at internal Iraqi events that might require/precipitate an American intervention (rather than dealing with the sort of invasion action actually undertaken by the US), the interagency group of participants produced a list of challenges the US would face that looks fairly prescient, given current events. Unfortunately, the exercise itself never made much of an impact. In 2003, when the then-retired Gen. Zinni called CENTCOM to recommend that they look at Desert Crossing again, they didn't know what he was talking about.
The point is not that the game predicted anything. Games don't predict very well, and generally should not be used for that purpose. What Desert Crossing did was bring together the right group of people in the right setting with the right procedural setup to allow them to thoroughly examine the right questions. But Desert Crossing is also an example of the difficulty of assimilating the results of such a game into an organizational context.