A cobalt bomb is a type of "salted bomb": a nuclear weapon designed to produce enhanced amounts of radioactive fallout, intended to contaminate a large area with radioactive material. The concept of a cobalt bomb was originally described in a radio program by physicist Leó Szilárd on February 26, 1950. His intent was not to propose that such a weapon be built, but to show that nuclear weapon technology would soon reach the point where it could end human life on Earth, a doomsday device. Such "salted" weapons were requested by the U.S. Air Force and seriously investigated, but not deployed. In the 1964 edition of the U.S. Department of Defense book "The Effects of Nuclear Weapons", a new section titled radiological warfare clarified the "Doomsday device" issue.