The purpose of this study was to investigate the underlying mechanisms that explain the influence of instructor support on attrition levels within Navy basic military training. Based on self-determination theory, we hypothesized that higher autonomy support leads to lower intent to quit, mediated by self-efficacy and training value. Results from a group of trainees (N. = 208) confirmed that autonomy support negatively predicted intent to quit and that this relationship was mediated by self-efficacy. Training value did not mediate between autonomy support and intent to quit. In addition, logistic regression showed intent to quit predicted attrition. In conclusion, the application of self-determination theory provided new insights into the mechanisms underlying attrition in the military domain. © 2013 Elsevier Inc.