For nearly 40 years a group of Washington's best minds on defense issues has met each Wednesday at the end of the day for a midweek happy hour in the basement of the Officers Club at spacious Fort Myer in Virginia, overlooking the Potomac River and the federal capital beyond. Participants on any given evening might include a French liaison officer, a Russian intellectual, several retired colonels, a former assistant secretary of defense and a budding journalist needing to be schooled in the intricacies of one of the Pentagon's newest weapons systems. As the beer flows, one knot of guests...