ommand, and con- trol. 2.4 A VIEWPOINT One can paint the following picture of the development of spread-spectrum communications. During World War II the Allies and the Axis powers were in a desperate technological race on many fronts, one being secure commu- nications. Jamming of communication and navigation systems was attempted by both sides and the need for reliable communication and accurate navi- gation in the face of this threat was real. One major AJ tactic of the war was to change carrier frequency often and force the jammer to keep looking for the right narrow band to jam. While this was possible to automate in the case of radar, communication frequency hopping was carried out by radio oper- ators, in view of the major technological problem of providing an accurate synchronous frequency reference at the receiver to match the transmitter. Thus, at least frequency hopping and, to a similar extent, time hopping were recognized AJ concepts during the early 1940s. Many of the early "secure" or "secret" non-SS communication systems seem to have been attempts to build analog equivalents of cryptographic machines and lacked the notion of bandwidth expansion (e.g., the Green Hornet, the Telefunken dual wheels system). The initial motivation for direct sequence systems appears, on the other hand, to have come from the need for accurate and unambiguous time-of-arrival measurements in navi- gation systems (e.g., WHYN and CODORAC), and from the desire to test or extend Shannon's random-signaling concept and, thus, communicate covertly (e.g., Rogoff's noise wheels experiment). The DS concept followed the FH and TH concepts by several years partly because the necessary cor- relation detection schemes were just emerging in the late 1940s. Who first took these diverse system ideas and recognized the unifying essential requirements of a spread-spectrum system (e.g., high carrier-to-data bandwidth ratio, an unpredictable carrier, and some form of correlation detection)? From the available evidence, it appears that Shannon 