This chapter addresses the critical need for reliability and fault tolerance in military IoT systems operating in dynamic, error-prone, and potentially hostile environments. It defines dependability attributes (reliability, availability, and safety) and links them intrinsically to security requirements. Fault scenarios specific to military IoT, encompassing hardware, software, and interaction faults, are analyzed. The chapter reviews fault-tolerant techniques, categorizing them into prevention and tolerance, with error masking techniques such as redundancy and consensus and non-error masking techniques such as monitoring, detection, and diagnosis. It emphasizes the integration of security with reliability mechanisms and assesses the applicability of techniques across military IoT architectural layers, noting limitations for real-time scenarios.