Modern ground surveillance microwave radar leverages MIMO, beam forming, AI, edge computing, cameras and a variety of sensor technologies for an advanced, comprehensive fusion-approach to threat detection. This article presents a review of developments in the field from early approaches to the present day, and highlights a number of contemporary solutions. MIMO has revolutionized spatial accuracy for environments with multiple targets. Beam forming significantly improves object detection accuracy. AI and edge computing in particular are transforming threat detection with sophisticated capabilities to address complex security scenarios reliably and intelligently.