The system technical features of a new class of multifunction rotating electronically scanned radar systems (RESRSs), that electronically scan in both azimuth and elevation while rotating in azimuth, are described in terms of satisfying modern air defense needs. A brief comparison to classical radar solutions is followed by use of an illustrative example to indicate quantitatively as well as qualitatively the advantages inherent in an RESRS design. The concluding portion of the paper contains descriptions and photographs of a modern class of recently fielded RESRSs for tactical air surveillance.