This series is composed of letters and memoranda drafted for McNamara by the Department of Information and Public Affairs (IPA) between January 1969 and July 1981. Letters consist of thank-you notes, mostly regrets, for invitations to participate or speak at meetings or luncheons, deliver interviews and appear on television, thanks for gifts, books, articles, comments, views, support, staff work, and responses to requests for material, statements and articles.

The addressees are private citizens, scholars, journalists, heads of organizations and congregations, diplomats, and government officials. Thank-you letters range from a note to President Leopold Sedar Senghor thanking him for a volume of poetry, to letters to the U.S. President, senators and congressmen thanking them for assuring the passage of foreign assistance legislation. Responses to inquiries include a letter informing President Sekou Toure of the progress of the Konkoure project, a letter attempting to answer William Safire's etymological inquiry about the phrase bargaining chip, and notes declining requests for comments on defense policy and the Vietnam War.