Ernest May, a distinguished Harvard historian of world wars, intelligence and international relations who became a senior adviser to the 9/11 Commission that analyzed the 2001 terrorist attacks in Washington and New York, died June 1 at a hospital in Boston. He had complications after surgery for cancer. He was 80. May taught at Harvard for 55 years, and he was a prolific writer, frequently working with other eminent historians of the day. He collaborated with John Hope Franklin and John Caughey on 'Land of the Free' (1965), a controversial eighth-grade history textbook that offered a frank look at America's history of slavery and denial of civil rights to African Americans, and with fellow Harvard historian Richard Neustadt on 'Thinking in Time: The Uses of History for Decision-Makers' (1986). May's scholarship frequently emphasized the effect decision makers had on history. In 2000, he wrote a revisionist history of the German occupation of France during World War II, 'Strange Victory: Hitler's Conquest of France,' in which he concluded that if not for the poor quality of France's military strategy, 'It is more than conceivable that the outcome would have been not France's defeat but Germany's.' In 2003, May was recruited to the 9/11 Commission by Philip Zelikow, whom May had encouraged to lead the commission. Zelikow, now a University of Virginia historian, had edited three volumes with May on President John F. Kennedy's presidential tapes, starting in 1997. Their work formed the basis for the Hollywood film 'Thirteen Days' (2000), starring Kevin Costner as an aide to Kennedy during the Cuban Missile Crisis. The 9/11 Commission was convened by Congress and included members of both major political parties as well as scholars and intelligence officials, with May and Zelikow serving as 'the architects of the report,' as May wrote in the New Republic. The commission's report framed declassified information about al-Qaida's attacks on Sept. 11, 2001, into a coherent narrative, and its authors wrote in its preface that the report sought to answer two questions: 'How did this happen, and how can we avoid such tragedy again?' Published in a mass-market paperback by W.W. Norton in 2004, the report sold millions of copies and was a finalist for the National Book Award. Author John Updike wrote in the New Yorker that it ranked with the King James Bible as 'our language's lone masterpiece produced by committee.' Many of May's years at Harvard were spent in the Kennedy School of Government, which was co-founded by Neustadt, and May's work was often aimed at policymakers. In a New York Times review of 'Thinking in Time,' Bernard Gwertzman wrote that May was 'advocating more and better use of history by those charged with making decisions.' At Harvard, May also served in posts including dean of the college, associate dean of the Faculty of Arts and Sciences and chairman of the history department. Zelikow told the New York Times, 'I think Ernest May is the most important scholar of American foreign relations to emerge during the second half of the 20th century.' Ernest Richard May was born Nov. 19, 1928, in Fort Worth, Texas. He was a 1948 graduate of the University of California at Los Angeles, where he also received a doctorate in history in 1951. He joined the Harvard faculty in 1954, after serving in the Navy Reserve and working as a historian for the Joint Chiefs of Staff. His marriage to the former Nancy Caughey ended in divorce. Survivors include his wife of 20 years, Susan Wood of Cambridge, Mass.; three children from his first marriage, John May of Wenham, Mass., Susan Rachel May of Syracuse, N.Y., and Donna May of Los Angeles; and three grandchildren. Knowing that part of his legacy rested on the 9/11 Commission Report, May wrote in the New Republic: 'I hope that this official report will not be the last government document of its kind. In these perilous times, there will surely be other events that will require the principles of historiography allied to the resources of government, so that urgency will sometimes become the friend of truth.' 