The Hulk is often viewed as a reaction to war. As well as being a reaction to the Cold War, the character has been a cipher for the frustrations the Vietnam War raised, and Ang Lee said that the Iraq War influenced his direction. In the Michael Nyman edited edition of "The Guardian", Stefanie Diekmann explored Marvel Comics' reaction to the September 11 attacks. Diekmann discussed The Hulk's appearance in the 9/11 tribute comic "Heroes", claiming that his greater prominence, alongside Captain America, aided in "stressing the connection between anger and justified violence without having to depict anything more than a well-known and well-respected protagonist." In "Marvel: Five Fabulous Decades of the World's Greatest Comics", Les Daniels addresses the Hulk as an embodiment of cultural fears of radiation and nuclear science. He quotes Jack Kirby thus: "As long as we're experimenting with radioactivity, there's no telling what may happen, or how much our advancements in science may cost us." Daniels continues, "The Hulk became Marvel's most disturbing embodiment of the perils inherent in the atomic age."