“…Understanding these etiological differences among military and postmilitary populations is critical both to providing effective screening, prevention, and treatment (Lincoln, Ames, & Moore, 2016) and to understanding the contexts for substance use cessation, maintenance, and escalation after military service, a topic of great importance established by the pioneering work of Lee Robins on Vietnamera opioid abuse and recovery (Robins, 1993; Robins, Davis, & Nurco, 1974; Robins, Helzer, Hesselbrock, & Wish, 2010; Robins & Slobodyan, 2003). This analysis offers an examination of opioid use initiation patterns among an Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND)-era cohort of formerly enlisted veterans, providing an epidemiological attention to how opioid use initiation differs by birth cohort (Novak, Bluthenthal, Wenger, Chu, & Kral, 2016) among different military cohorts which came of age during different national drug epidemics (Golub & Johnson, 2001; Golub, Johnson, & Dunlap, 2005; Musto, 1993) and, accordingly, may have initiated and continued to use opioids in different ways.…”