Departures of note

John Riley, an Irish-born soldier who had deserted the U.S. Army before the Mexican-American War officially began, led a band of fellow defectors into the Mexican Army, forming the Saint Patrick's Battalion. At the Battle of Churubusco in 1847, the unit made a last stand on the outskirts of Mexico City; about 35 members were killed and 85 captured, including Riley. Because he had deserted before the U.S. declared war, he was not sentenced to death at his court-martial, but was branded on the cheek with the letter 'D' for deserter.

Born around 1817 in Clifden, County Galway, Riley served in the British Army before emigrating to Canada and then the United States, where he enlisted in the U.S. Army in Michigan. In 1846, he and Patrick Dalton deserted and joined the Mexican forces, eventually forming the Saint Patrick's Battalion, composed mostly of Irish and German immigrants and other Catholics. Riley testified that he deserted because of discrimination and mistreatment of Irish Catholics in the U.S. Army and anti-Catholicism he encountered in the United States.

After his conviction and branding, Riley was released and rejoined the Mexican forces, reportedly growing his hair to conceal the scars. He continued serving in the regular Mexican Army after the war, confirmed as a 'Permanent Major' and stationed in Veracruz, where he was retired on medical grounds on 14 August 1850 after suffering from yellow fever. A death certificate found in Veracruz records the burial of a 'Juan Reley' on 31 August 1850, but scholars have cast doubt on whether this was Riley, noting discrepancies in age, his known sobriety, and his recent discharge with pay and medals.

A bronze sculpture was erected in Riley's birthplace of Clifden, Ireland, as a gift from the Mexican government to commemorate him and the Saint Patrick's Battalion. His story has also been portrayed in the 1999 film One Man's Hero, with Tom Berenger as Riley, and in a 2011 documentary on the Irish television channel TG4.