Does early-life trauma influence battlefield behavior? Evidence from Irish regiments in the American Civil War shows that experiencing the Irish Potato Famine more than a decade earlier made soldiers more likely to desert.

📌 Who was examined and how exposure was identified

• Focus is on Irish troops in the American Civil War who lived through the Potato Famine as children.
• Famine exposure is measured within the Irish group at the individual level using multiple complementary indicators:
• birth cohorts (timing of birth relative to the famine),
• sibling birth order (within-family variation in exposure),
• adult height (a biological marker of early-life deprivation), and
• the geography of surnames in Ireland (linking recruits to local famine severity).

📊 How battlefield behavior was linked to early hardship

• Each measurement strategy consistently indicates that greater famine exposure is associated with higher rates of desertion among Irish soldiers.
• Observable implications from a formal theory of behavior under threat were developed and tested against the data to adjudicate mechanisms.

📈 Key findings and the mechanism

• The most plausible mechanism explaining higher desertion is heightened risk aversion stemming from early-life trauma.
• The famine effect on desertion weakens and effectively disappears once soldiers are socialized into active combat roles through collective risk-sharing (suggesting social integration into combat mitigates the early-life influence).

💡 Why this matters

• Illuminates how nonpartisan, early-life atrocities can leave lasting behavioral legacies that shape contentious behavior in later conflicts.
• Highlights the importance of pre-migration experiences for soldiers drawn from migrant-sending populations.
• Demonstrates the value of combining demographic, biological, and geographic within-group measures to identify long-run behavioral effects of childhood shocks.