Originally and in most iterations of the creature, Godzilla is a colossal prehistoric reptilian or dinosaurian monster that is amphibious or resides partially in the ocean, awakened and empowered after many years by exposure to nuclear radiation and nuclear testing. With the nuclear bombings of Hiroshima and Nagasaki and the Lucky Dragon 5 incident still fresh in the Japanese consciousness,[29] Godzilla was conceived as a metaphor for nuclear weapons.[30] Others have suggested that Godzilla is a metaphor for the United States, a "giant beast" woken from its "slumber" that then takes terrible vengeance on Japan.[31][32][33] As the film series expanded, some storylines took on less serious undertones, portraying Godzilla as an antihero or lesser threat who defends humanity. Later films address disparate themes and commentary, including Japan's apathy, neglect, and ignorance of its imperial past,[34] natural disasters, and the human condition.[35]