The role of the Risk Management Framework (RMF) Information Systems Security Engineer (ISSE) has never been more crucial in today's evolving cybersecurity landscape. This book serves as a practical guide for professionals in Information Assurance and Governance, Risk, and Compliance (GRC) within the Defense Industrial Base (DIB) and Federal Civilian Departments and Agencies, as well as those looking to understand the RMF ISSE's responsibilities. Rather than an exhaustive reference, it focuses on the first five (5) steps of NIST Special Publication 800-37 Revision 2, examining them through the lens of the Systems Development Lifecycle (SDLC) to provide a structured approach to securing information systems.