This document establishes the requirements for systems engineering activities to be performed on projects of defense agencies, including the United States (US) Department of Defense (DoD), across the entire system life cycle. This document implements ISO/IEC/IEEE 15288:2023, Systems and software engineering —System life cycle processes, for use by defense agencies in acquiring systems or systems engineering support, including the planning, acquisition, operation, modification, and sustainment of defense systems. Within the context of ISO/IEC/IEEE 15288:2023, this document provides detailed requirements for the application of the life cycle processes, activities, and tasks for use on any defense system. It includes the effective integration of agreement processes, technical processes, technical management processes, organizational project enabling processes, and essential specialty engineering requirements. While primarily supporting the acquirer-supplier agreement mode, this document also can be used to support other modes, including use by organizations, projects, and process assessors.