Radiological warfare is any form of warfare involving deliberate radiation poisoning or contamination of an area with radioisotopes, but without the use of nuclear weapons. While radiological weapons were researched and in some cases tested during the Cold War, there is no evidence any military has ever deployed operational radiological weapons, although they have been used for assassination.
Nuclear warfare, both via fission and fusion weapons, creates radioisotopes in the form of fission products and neutron-activated surface material. This fallout is incorporated into military planning. Neutron bombs are designed to maximize the lethal radiation area and minimize the blast. These uses are generally not considered direct radiological warfare, but salted bombs, which maximize radioisotope production in a nuclear blast, are.