David Dean Rusk (1909-94) was the United States Secretary of State from 1961 to 1969 under presidents John F. Kennedy and Lyndon B. Johnson. Early in his tenure, Rusk had strong doubts about US intervention in Vietnam, but later his public defense of US actions in the Vietnam War made him a frequent target of anti-war protests.
“Rusk, inherited by LBJ, was a firm supporter of the war in Vietnam. He was a pale, rather expressionless individual, and I found John's description apt and witty. I don't know why he misspelled the name; I don't think there was any danger of prosecution to worry Macmillan. John probably liked the idea of suggesting that he was empty as well as pasty."