Force XXI is the Army's ongoing process to define the Army of the next century. The current codification of Force XXI is in TRADOC PAM 525-5 dated 10 December 1993. RAND was asked to apply its Assumption-Based Planning (ABP) methodology to that version to assess its robustness into the future. Because Force XXI is an incomplete plan at this point, ABP was modified to include a "rationalization" step that attempts to connect the Force XXI assumptions about the future with the actions it recommends. Unconnected assumptions indicate actions yet to be specified. The remaining assumptions were judged (in conjunction with Army planners) for vulnerability in the coming decades. A variety of important vulnerabilities are highlighted in this documented briefing, the most significant of which relates to operations other than war (OOTW). The Army has much work ahead to develop a robust plan for future OOTW operations.
Dewar, James A., Jeffrey A. Isaacson, and Maren Leed, Assumption-Based Planning and Force XXI. Santa Monica, CA: RAND Corporation, 1997. https://www.rand.org/pubs/documented_briefings/DB172.html. Also available in print form.
Dewar, James A., Jeffrey A. Isaacson, and Maren Leed, Assumption-Based Planning and Force XXI, Santa Monica, Calif.: RAND Corporation, DB-172-A, 1997. As of July 15, 2021: https://www.rand.org/pubs/documented_briefings/DB172.html