One more point. They weren't going to shoot just one at the Pentagon, they were going to shoot/drop/lob/whatever 50 of the suckers. Same with the rest of Washington, New York, Philadelphia (ouch, that hurts), Houston, Chicago, ect. The point that most nuclear war strategy falls down is in the number of warheads whizzing around out there (both ways). If (and it is a big if but once the missles start flying it becomes an eventuality not an if) there is a probability of failure as high as 20% (and I have heard similar numbers) then the way to make sure that there is no chance of failure is to launch enough to make the probability of failure irrelevent.
That is why Civil Defense in the Nuclear Era was essentially an exercise in futility. With stockpiles of bombs/warheads in the tens of thousands, the primary targets would've been obliterated even if half the warheads missed. The bombs just would've kept coming and not getting killed would've been a function of luck more than planning.