Major Gen. John K. Singlaub
John Kirk Singlaub (born July 10, 1921) is a highly decorated former OSS officer, a founding member of the Central Intelligence Agency (CIA), and a retired Major General in the United States Army. In 1977 Singlaub, was relieved from his position as Chief of Staff of U.S. forces in South Korea after criticizing President Jimmy Carter's decision to withdraw U.S. troops from the Korean peninsula in an interview with the Washington Post. Less than a year later Singlaub was forced to retire after publicly questioning President Carter's national security policies. In 1979 Singlaub founded the Western Goals Foundation, a private intelligence network that was implicated for supplying weapons to the contras during the Iran-contra affair. Singlaub is a contributing author to several books and is the author of his autobiography as well as numerous articles. . .
Gen. Singlaub is still alive at 94. He is 3 years older than Jimmy Carter—maybe he is determined to outlast him.
My belief, and I'm not sure where I read it, is that the Founders had a problem with military officers swearing allegiance to any individual.
Of course, the UCMJ has more than enough provisions to dissuade officers from butting heads with the President.