This study prospectively examined psychological strengths targeted in U.S. Army training programs as predictors of psychiatric diagnosis in active duty soldiers. At baseline, the cohort (140,584 soldiers) was without psychiatric disorder. Soldiers were then followed for 2 yr and classified as healthy, or acquiring a psychiatric diagnosis (adjustment disorder, anxiety disorder, depression, or post-traumatic stress disorder), or being prescribed psychotropic medication without a psychiatric diagnosis. Soldiers who remained healthy reported significantly higher strengths scores at baseline, compared with soldiers who were diagnosed with a psychiatric disorder. In addition, soldiers in the worst strengths decile were twice as likely to develop a psychiatric disorder, compared with soldiers in the top 50% on baseline strengths. Strengths afforded the greatest protection against depression. Offering tailored resilience training programs could help the Army steel vulnerable soldiers against the challenges of life, military training, and combat.