Assessment is the continuous cycle whereby assessors observe and evaluate the everchanging operational environment to inform decisions about the future and make operations more effective than those of the past. Done properly, assessment enables a shared understanding between relevant stakeholders and decision makers, ensuring unity of effort and purpose. Successful assessment integration into the operations process gives commanders a means to proactively identify and adjust to emerging opportunities and risks to mission accomplishment. Timely recognition of opportunities and risks affords commanders a distinct advantage by possibly catching the enemy off balance and rapidly ending a battle; refocusing joint force capabilities to minimize disruption; or hastening accomplishment of objectives, conditions, and end states. Conversely, missed opportunities and risks result in protracted engagements, higher casualties, increased potential for tactical defeat, and operational and strategic setback. Of the three major military operational functions described in joint doctrine (plan, execute, and assess), doctrine associated with assessment is the least described and understood. Military organizations exert extensive effort planning and executing operations yet devote comparatively little effort in developing a structured method to identify indicators of success or lack of progress. Recent military operations experienced significant challenges conducting operation assessment. Few documented assessment successes exist, with those successes achieved only after much effort and revision. A lack of doctrine providing guidance and discussion of the practical activity necessary to integrate assessment into the operations process was a contributing factor to this lack of success. Complex, ill structured, and adaptive operating environments quickly overwhelmed existing assessment doctrine, leaving units struggling to achieve situational understanding and inform decision-making. Hybrid threats and non-nationstate actor proliferation, in the current operational environment, virtually ensures continued assessment difficulty in the future. Chapter I clarifies disparate assessment terms of reference to enable effective communication. Chapter II discusses assessment, defines operation assessment, discusses considerations for organizing a headquarters to conduct assessment, and suggests roles and responsibilities for commanders and staff officers in operation assessment. Chapter III describes an assessment framework that is adaptable to any missionspecific need. The discussion centers on how assessors might organize and compartmentalize the operational environment, analyze data, and communicate the assessment to a decision maker. The chapter concludes with four examples illustrating assessment framework adaptations from recent operations. Chapter IV describes prerequisites for effective assessment planning, and suggests a three-step procedure to guide it. This chapter concludes with an example of an assessment plan and a corresponding example of an assessment annex to an operations order. Chapter V associates assessment activity with appropriate operations and planning process activity, and describes the best practice for integrating assessment into the operations process and the commander's decision cycle. Appendix A describes considerations for developing effective measures, and discusses the iterative nature of measuring and the importance of applying professional military judgment to identify trends. This appendix suggests proven measures for consideration during assessment plan development and offers procedures for developing each. Appendix B describes ill structured and complex adaptive systems in the operational environment. It discusses the implications of complexity for operation assessment and offers suggestions for adapting the assessment framework in ill structured and complex adaptive operational environments.