With a promise of US citizenship, they joined the American army, but during the war they defected, joining the Mexican side and fighting alongside the Mexicans who would ultimately lose the war.
Most of those who survived were court-martialed and executed by hanging by the US military.
A few Mexican Irish communities existed in Mexican Texas until the Texas Revolution. The Batallón de San Patricio was a largely (ethnically) Irish battalion of U. troops who deserted and fought alongside the Mexican Army against the United States in the Mexican–American War of 1846 to 1848.
Many Irish then sided with Catholic Mexico against Protestant pro-U. Álvaro Obregón (O'Brien) was president of Mexico during 1920-24 and Ciudad Obregón and its airport are named in his honor.
Viva Aerobus is the country’s regional low-cost airline, part-owned by the Ryan family, who founded Ryanair.