On the whole the film is very accurate, being based on the book The Kennedy Tapes, which contains transcripts of many of the meetings and telephone calls between President Kennedy and his advisers during the Cuban Missile Crisis. The role of presidential adviser Kenneth O' Donnell, played by Kevin Costner in the film, was inflated as a dramatic device; in reality he played no significant part in resolving the crisis. The film's portrayal of many Kennedy cabinet members, such as Robert MacNamara, has been criticised as overly shallow by some, as has the depiction of the U.S. Military as being aggressively and almost cartoonishly gung-ho about attacking Cuba. Indeed, the US military, which routinely extends cooperation to film-makers through the provision of military hardware and personnel for use in films, refused to assist in the making of Thirteen Days because of unhappiness about the unsympathetic portrayal of air force general Curtis LeMay. As a result, computer graphics and old stock footage were used to fill in the gaps where genuine military equipment might otherwise have been used.