expeditionary forces (DEFs-BCTs trained for known operational requirements), ready expeditionary forces (REFs-BCTs that form the pool of available forces for short-notice missions) or contingency expeditionary forces (CEFs-BCTs earmarked for contingency operations). Based on their commanders' assessments, units would move to the ready force pool, from which they could deploy should they be needed, and in which the unit training focus would be at the higher collective levels. Units would enter the available force pool when there is approximately one year left in the cycle, after validating their collective mission-essential task list proficiency (either core or theater-specific tasks) via battle-staff and dirt-mission rehearsal exercises. The available phase would be the only phase with a specified time limit: one year. Not unlike the division-ready brigades of past decades, these formations would deploy to fulfill specific requirements or stand ready to fulfill short-notice deployments within 30 days. The goal was to generate forces 12–18 months in advance of combatant commanders' requirements and to begin preparing every unit for its future mission as early as possible in order to increase its overall proficiency. Personnel management would also be reorganized as part of the Army transformation. Previously, personnel was managed on an individual basis in which soldiers were rotated without regard for the effect on unit cohesion. This system required unpopular measures such as "stop loss" and "stop move" in order to maintain force levels. In contrast, the new personnel system would operate on a unit basis to the maximum extent possible, with the goal of allowing teams to remain together longer and enabling families to establish ties within their communities. Abrams 2016 noted that mid-level Army soldiers found they faced an unexpected uptempo in their requirements, while entry-level soldiers in fact welcomed the increased challenge. Readiness model ARFORGEN, "a structured progression of increased unit readiness over time, resulting in recurring periods of availability of trained, ready, and cohesive units prepared for operational deployment in support of geographic Combatant Commander requirements" was utilized in the 2010s. ARFORGEN was replaced by the Sustainable Readiness Model (SRM) in 2017. In 2016 the 39th Chief of Staff of the Army identified the objective of a sustainable readiness process as over 66 percent of the Active Army in combat ready state at any time; in 2019 the readiness objective of the National Guard and Army Reserve units was set to be 33 percent; Total Army readiness for deployment was