This anthology of senior participants' observations of the Decisive Action Training Environment serves two functions. First, it is explicitly a teaching tool for the operating force to use in preparing commanders and units for an expeditionary future against a hybrid threat. Second, it is itself an artifact, reflecting the current understanding of Army doctrine by its practitioners during a time of turbulence in the force, uncertain resources and a comprehensive re-engineering of that doctrine. For that reason, some usages may not perfectly accord with doctrinal definitions, and others are not found in doctrine at all. We have nevertheless chosen to retain them for the reader's benefit as an indirect lesson on the complexity of the Army's task going forward from the wars in Iraq and Afghanistan.