Gus Martin's Understanding Homeland Security, 4th edition offers much-needed insight into the complex nature of issues surrounding modern homeland security. This comprehensive textbook examines the theories, agency missions, laws, and regulations governing the homeland security enterprise through the lens of threat scenarios and countermeasures related to terrorism, natural disasters, emergency management, cyber security, and much more. Martin's pedagogical approach is designed to stimulate critical thinking in readers, allowing them to not only comprehend the fundamentals, but to analyze and respond to various threat environments. The Fourth Edition introduces readers to homeland security in the modern era, focusing particularly on the post - September 11, 2001 world. Exploring cutting-edge topics, this book keeps readers on the forefront of homeland security.