Asymmetric or stateless warfare presents major challenges to the U.S. and its allies for developing effective defense and responses. Programs in APL’s Homeland Protection Business Area represent critical contributions spanning a broad range of needed technologies and systems. We apply a strong systems engineering discipline to programs that support primarily the Departments of Defense and Homeland Security. These efforts encompass protecting and deterring terrorist-type attacks, responding to threats and hazards, reducing vulnerabilities, limiting potential damage, and enhancing response and recovery. Our focus is on helping sponsors solve immediate problems, while continually looking ahead to identify the next threats and the countering technologies to foil them.