The United States is at risk of developing a cadre of military leaders who are cut off politically, culturally and geographically from the population they are sworn to protect, Defense Secretary Robert M. Gates told an audience at Duke University on Wednesday night.

In a speech aimed at addressing what he sees as a growing disconnect between the country as a whole and the relatively few who fight its wars, Mr. Gates said that although veterans from Iraq and Afghanistan were embraced when they came home, “for most Americans the wars remain an abstraction — a distant and unpleasant series of news items that do not affect them personally.”

Even after Sept. 11, 2001, Mr. Gates said, “in the absence of a draft, for a growing number of Americans, service in the military, no matter how laudable, has become something for other people to do.”