The Chemical Corps is the branch of the United States Army tasked with defending against chemical, biological, radiological, and nuclear (CBRN) weapons. The Chemical Warfare Service was established on 28 June 1918, combining activities that until then had been dispersed among five separate agencies of the United States federal government. It was made a permanent branch of the Regular Army by the National Defense Act of 1920. In 1945, it was redesignated the Chemical Corps.