Petraeus’ command of coalition forces during the Surge in Iraq has been widely lauded. In his book "The Savior Generals" historian Victor Davis Hanson wrote, "...that without David Petraeus, the American effort in Iraq—along with the reputation of the U.S. military in the Middle East—would have been lost long ago." In her introduction of Petraeus at the Baccalaureate ceremony for the Class of 2009, Princeton University President Shirley Tilghman described his accomplishments. While acknowledging that much remains to be accomplished in Iraq, Tilghman paid tribute to Petraeus's "leadership in rethinking American military strategy through his principles of counterinsurgency", which are, she said, "eliminating 'simplistic definitions of victory and defeat in favor of incremental and nuanced progress'".