Research on leadership emergence has mainly focused on adulthood and relied on retrospective accounts of childhood factors. Based on a prospective cohort study of 7719 boys born in 1953, of which 5928 were later drafted, we explored individual differences in leadership emergence in childhood and early adulthood. The data set consisted of register data from different time points and a survey of the cohort in the 6th grade. As expected, cognitive ability, tallness and muscular power were decisive for assessment of military officer suitability. However, we also found a moderate to strong impact on this assessment score from social class, leadership aspirations in childhood, birth order, self-regulatory skills in school, parental support, and previous participation in extracurricular activities. Similarly, social class, cognitive ability, developmental experiences, and birth order were important for nominations as class party organizer in the 6th grade. Delay of gratification was not associated with these nominations at all and was neutralized by cognitive ability in relation to officer suitability. The results strongly support a life-cycle approach to leadership emergence.