"An essential guide to counterintelligence, blending theory with case studies to fill a crucial gap in the intelligence literature. Both insightful and accessible, this book offers a rare, practitioner-driven perspective for anyone keen to explore the intricacies of CI." —Giangiuseppe Pili, James Madison University What is the core purpose of counterintelligence? What does it involve? To answer these questions, Kevin Riehle explains in detail how counterintelligence analysis supports the mission of thwarting adversaries—how a foreign entity's intelligence cycle can be exploited, disrupted, or manipulated—in order to gain decision advantage. Case studies of operations involving the Soviet Union and Russia also illustrate how counterintelligence-derived information can support broader US national security decisionmaking.