The military is described as a social context that contributes to the (re-)initiation or intensification of cigarette smoking. We draw on data from the 1985-2014 National Survey of Drug Use and Health (NSDUH) and the Wisconsin Longitudinal Study (WLS) to conduct complementary sub-studies of the influence of military service on men's smoking outcomes across the life course. Descriptive findings from an age-period-cohort analysis of NSDUH data document higher probabilities of current smoking and heavy smoking among veteran men across a broad range of cohorts and at all observed ages. Findings from sibling fixed-effects Poisson models estimated on the WLS data document longer durations of smoking among men who served in the military and no evidence that selection explains the observed relationship. Together, these results provide novel and potentially generalizable evidence that participation in the military in early adulthood exerts a causal influence on smoking across the life course.