To an outsider, it may seem a mere bureaucratic blip that Gen. David Petraeus was called back from Iraq last week to chair the promotion board that picks the Army's next new one-star generals. But, in fact, the story (first reported by Ann Scott Tyson in the Washington Post) is a very big deal—potentially the first rumble of a seismic shift in the very core of the U.S. military establishment.

The promotion board is the vehicle through which the Army's dominant culture is perpetuated—a behind-closed-doors committee of 15 generals that each year selects the 35 to 40 colonels (out of 1,000 applicants) who rise to the rank with stars. As with all gateway panels in every profession, the members of this board are inclined, if not explicitly motivated, to seek candidates in their own image—officers whose careers look like theirs.

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"Everyone studies the brigadier-general promotion list like tarot cards. It communicates what qualities are valued and not valued." If innovative officers see that their innovations are not valued, they'll either conform or leave.