As in the labor force as a whole, military recruits typically begin their careers with deficiencies in at least some soft skills relevant for workplace success (e.g., accepting feedback, collaboration, integrity, self-awareness). While many may assume that soft skills can be developed naturally as enlistees gain experience on the job, certain soft skills may prove more resistant to change than others. The current study quantitatively compares the relative malleability of distinct soft-skill competencies in an Air Force context. Specifically, we evaluate the development of first-term airmen on 17 distinct organizationally valued soft-skill competencies based on the perceived proficiency of first-term airmen (in aggregate) at two career milestones. Estimated change in competency proficiency is based on survey ratings from 1,059 technical training instructors and 6,894 first-line supervisors on the competency proficiency of first-term airmen (a) upon completion of technical training and (b) at the end of their four-year enlistment. Results are interpreted through a framework of developmental difficulty theory previously tested only in the context of the short-term development of midcareer professionals. Implications for the prioritization of certain competencies in screening and personnel selection are discussed.