Who was the worst Secretary of Defense?

[The Duke]

People forget Rumsfeld's first tour as SecDef in the 1970s, which was a great success.  People also forget the importance of Rumsfeld's base realignment, moving us away from a focus on Europe.

And Supersoulty is right about McNamara in the Cuban Missile Crisis.

In my view, neither of these guys is the worst SecDef ever.  I'd say the worst SexDef ever was Les Aspin.