The Stochastic Active Reserve Assessment (SARA) Model: Force Planning under Uncertainty

The Department of Defense (DoD) is responsible for preparing the Armed Forces for a future that is fundamentally uncertain—indeed, that is unknowable. DoD has typically assessed future needs and capabilities based on representative planning scenarios. This approach has the strength of providing a common focus across DoD on a few agreed upon situations. However, such an approach has limitations, because decision making in the face of uncertainty requires evaluating implications across a distribution of possible future events. The Institute for Defense Analyses’ Stochastic Active-Reserve Analysis (SARA) model is intended to augment DoD’s existing formal planning construct as a tool for assessing alternative force structures that can provide an analytical basis for DoD resource allocation decisions.This model was originally built for the Office of the Secretary of Defense, Cost Assessment and Program Evaluation (OSD CAPE) with the intention of analyzing the tradeoffs between alternative active-reserve mixes when demand is uncertain. However, it can be used to examine many total force mix issues. We constructed the model as a framework in which a user provides inputs that answer several questions. On the demand side, the questions include the following: