“There are known knowns, things we know that we know; and there are known unknowns, things that we know we don't know. But there are also unknown unknowns, things we do not know we don't know.”

American politician and businessman

Donald Rumsfeld was an American politician, businessman, naval officer, and diplomat. Born in 1932, he served as U.S. secretary of defense under Gerald Ford and again under George W. Bush, becoming both the youngest and the oldest person to hold that office. He also served in Congress for Illinois for four terms, then held a series of senior roles in Washington, including director of the Office of Economic Opportunity, counselor to the president, U.S. representative to NATO, and White House chief of staff. Between his two Pentagon tenures, he led several companies as chief executive and chairman.