Read about Kullback on Wikipedia.
The oral history is on the NSA website over here.
Loads of cryptanalysis anecdotes therein (if you’re into that kinda thing), e.g., (p. 119):
There used to be coke machines, the Army version of the coke machines, I guess. You put in a nickel and a cup would come and you would get a coke. Well, it wasn’t long before the people discovered that the machine, when you dropped a coin in, would turn on. But if you pull the plug out, the mechanism which turned it off failed to operate. So people would go in there and put in their nickel and get a cup, pull the plug out and everybody in the wing would go get their cup of coke. So after a while, the vendor who filled these machines sort of looked at it and began to complain to General Corderman about the fact that here is a machine at the end of a day, all of the cokes and so on were used up and gone but he only finds a couple of nickels in it. “What gives?” I guess eventually Corderman checked and found out about the fact that people had found out that if you pull the plug once the machine got started then the mechanism which shut it off would fail. So he sent out a very cute notice to everybody in the Arlington Hall Station. It said, “Now that we have solved the machine and have enjoyed some of the fruits of that solution, I think we ought to provide the vendor with a nickel for each cup of coca cola.”