Mea culpa. Colin Powell, contrary to my assertion here, was correct in referring to Gen. George C. Marshall as the Secretary of Defense. As Joe Biles noted in a comment on my post, Gen. Marshall served as secretary of defense after his stint as President Truman's secretary of state. I should have known better than to question a former secretary of state and former chairman of the Joint Chiefs of Staff on that point.
While we're at it, it might be worth noting that Marshall was SecDef #3 under President Truman. Truman, the first to have a secretary of defense (following the major defense reorganization that occurred in 1947), appointed four before he was through. That remains the record for most secretaries of defense in a single presidential administration.
The record for the fewest number of secretaries of defense in a single administration is, of course, one. George W. Bush is the longest-serving president never to have changed his secretary of defense. (John F. Kennedy, Gerald Ford, Jimmy Carter, and George H. W. Bush are the other presidents to have had only one SecDef.) Robert S. McNamara, who served under JFK and LBJ from January 21, 1961 to February 29, 1968, is still the longest-serving secretary of defense. Donald H. Rumsfeld will, if he makes it, break McNamara's record sometime in late December of this year by virtue of having served for a year and two months under Gerald Ford.
I'm glad we got that cleared up.