But I didn't come to Stanford immediately. My first year at Stanford was actually spent on leave of absence in Princeton, New Jersey. Now this was the time of the Vietnam War, some of you might remember, and… and great ferment on campuses.  And the… and I had been deferred from the draft because of being a graduate student, at… at first, and because of being married, and having bad eyesight, and… though I was 4F for a while.  And then I, anyway, I… I… but I felt that I owed something to the United States for providing me with the… the freedom to be able to study, and… and not have to carry guns and defend my territory.  So… so I thought it would be good to… to give at least a year of National Service.  So I… so I said, well what could a person with my skills do for the country? And the answer was, you know, I was recruited into working for code-breaking, cryptanalysis, where people like Marshall Hall, my advisor, had, and other people at Caltech were… were prominent, because the combinatorial math that I was doing was useful in making and breaking codes. So then I… so I went there, and I worked not at the Princeton University, but at the Institute for Defense Analyses, which had a… which had a building on the... on the Princeton campus, called von Neumann Hall, actually.

And we… and I… I worked there on classified work with… with some tremendously excellent colleagues.  And the… the way we did it there was that half of… half of our time was supposed to be doing pure mathematical research, and half of it was supposed to be doing this classified work that… that is relevant to code breaking.  And in our case we were… most of us were also especially good at computer programming, so we would try to make computers… computer programs that could help in code breaking. The… the work there was secret; I… I still haven't been able to tell my wife what I was doing that year. And although I met a lot of great people that year, I found out that the… the secret life is not for me. I'm the kind of person that likes to talk about what I'm doing, and explain and teach, so… so I worked… I worked hard at helping that agency for a year, but then I… I knew that I should really be an academic, and not… no more do classified work after that… after that time. And so I can't tell you much… much about that… about that period, except that the people that I worked with were… were super.

And I published also some papers that… with people that I… that I worked with… my… my roommate there, Ed… Ed Bender, and I solved the famous problem in combinatorics where we were able to take what's called plane partitions and find a reason why the number of plane partitions of n is… has… has an amazingly simple form.
 
The plane partition is… you can understand it like this. Suppose you have 100 sugar cubes, and you want to put them into a box, and you… and you pack it solid against one of the corners of the box, how many ways are there to do that? And… and a… a man named Percy McMahon had… McMahon – M C M A H O N – had spent many years of his life solving this problem.  And the answer that he got was that there was a fairly simple formula explaining how many ways there are to put n sugar cubes into the corner of a box. But nobody knew a… a reason why it should be so simple.  And Ed Bender and I were roommates, and we… we spent a lot of our free research time thinking about this problem, and… and lo and behold we… we came up with a solution. And… and Ed and I… Ed is the person who sort of most perfectly blends his research skills with mine, in the sense that the two of us together… I… I never worked together with any… any other person on my life where… where we were, sort of, such an ideal team. That is, his… his strong points would complement my weak points, and… and my weak points would complement, you know, his strong points… my strong points would complement his weak points and his… vice versa, and we could… we could talk to each other at the same rate and… and understand each other at the same rate.  And so… so here we are in the same room, solving the problem together, and we each are… are going to take the next step, and we're getting somewhere. I never met anybody else who… where we were so perfectly attuned this way. In fact, it's so… it was such a good match that we're afraid to meet each other now, because we… we know that if we get together we have a responsibility to the world to invent some… some new idea, and that's too much of a responsibility, you know, it exhausts us, so… so we haven't seen each other for years. But when we were doing it though… it… we were really hitting it off well. And we… we solved this problem about plane partitions during the time I was in Princeton.