In 1973, after returning from five and a half years of captivity in Vietnam, John McCain spent nine months at the National War College, engaging in what he has described as "a private tutorial on the war, choosing all the texts myself, in the hope that I might better understand how we came to be involved in the war and why, after paying such a terrible cost, we lost." Thinking that this could be a Rosetta Stone for McCain's foreign policy evolution, and for his potentially conflicting feelings about his own arduous service in Southeast Asia, I sought his thesis paper via Freedom of Information Act. The results (which came too late for my book, though I write about it in the forthcoming paperback) were different than advertised: It was basically a meditation not on How We Got Involved in Vietnam, but rather on the practical efficacy of the military's code of conduct governing prisoners of war. I wrote about the paper briefly for reason here, and more expansively for the L.A. Times here.
The New York Times asked me for a copy of the paper a while back, and I handed it over. You can read the Gray Lady's write-up here.
Another interesting artifact of his thinking at the time can be found in this 12,000-word U.S. News & World Report essay he wrote in May 1973.