The worst Secretary of Defense since I have been alive is McNamara and I am 67!
Robert Strange McNamara is an "American?" business executive and a former (heavy on the former) United States Secretary of Defense.
McNamara served as Secretary of Defense from 1961 to 1968, during the Vietnam War period.
I was around for McNamara's stint, and I remember Viet Nam, although it is only now that I fully understand all of the horrible mismanagement and despicable 5th-column media intervention that attended that war.