Simplify the following text for a Grade 9 native English-speaking person.
Original: Robert Strange McNamara ( born June 9 , 1916 , in Oakland , California ) is an American business executive and former United States Secretary of Defense . McNamara served as Defense Secretary from 1961 to 1968 , during the Vietnam War .
Simplified: Robert Strange McNamara ( June 9 , 1916 -- July 6 , 2009 ) was an American business executive and the eighth Secretary of Defense , serving under Presidents John F. Kennedy and Lyndon B. Johnson from 1961 to 1968 , during which time he played a large role in escalating the United States involvement in the Vietnam War .