ACTIVE DEFENSE: Prentiss described Active Defense in 1941 as positive actions (as opposed to the negative actions of Passive Defense) carried out by the armed forces with the intent of engaging and defeating attacking enemy aircraft. Active Defense components included an air warning service, air defense fighters, antiaircraft artillery, and captive balloon barrages. Writing in 1951 Prentiss expanded this list based on World War II experience and wartime developments in new technology to include radar and large area smoke blankets.
Prentiss, Augustin M., Civil Air Defense, New York, NY, McGraw-Hill Book Company, Inc., 1941. Prentiss, Augustin M., Civil Defense in Modern War, New York, NY, McGraw-Hill Book Company, Inc., 1951.