Lead: During the Mexican War a group of American deserters composed an artillery unit in the Mexican Army, St. Patrick's Battalion. Intro: A Moment in Time with Dan Roberts. Content: Led by John O'Reilly a native-born Irishman and made of Irish ex-patriots, some former slaves, and not a view American abolitionists fearful that the Mexican War was a plot to increase the number of slave states, the San Patricios or St. Patrick's Battalion formed themselves into a highly effective, mobile artillery unit. Loading... Taking too long? Reload document | Open in new tab Download [5.75 KB] Share