 As a result, Puerto Ricans have participated in every war involving the United States from World War I onward.Thousands of Puerto Ricans participated in these wars Many lived and returned to their homeland, others were less fortunate and either died as a result of a hostile enemy action or were listed as MIA (Missing In Action).Missing In Action (abbreviated MIA) is a term (dating from 1946) referring to a member of the armed services who is reported missing following a combat mission and whose status as to injury, capture, or death is unknown.