Final answer:
Irish men who served as mercenaries in the arms were associated with the Irish Republican Army (IRA) during World War I. Some American units, such as the 369th Infantry, fought under French leadership and were recognized for their service.
Step-by-step explanation:
During World War I, Irish men who served as mercenaries in the arms were associated with the Irish Republican Army (IRA) and fought against British rule. The Irish War of Independence, which began in 1918, involved groups like Sinn Féin and the IRA who fought for an independent Ireland. While the majority of 4 million Americans who joined the military during the war saw no combat action, there were some American units, such as the 369th Infantry (also known as the 'Harlem Hellfighters'), who fought under French leadership and earned recognition for their service.