The Irish Brigade was an infantry brigade, consisting predominantly of Irish immigrants, that served in the Union Army in the American Civil War. The designation of the first regiment in the brigade, the 69th New York Infantry, or the "Fighting 69th", continued in later wars. They were known in part for their famous warcry, the "faugh a ballagh", which is an old Gaelic phrase, fág an bealach, meaning "clear the way
Formation of the ethnically based brigade served three Union purposes: 1) It warned Britain (which appeared to be favoring the Confederacy, if not deliberating entry into the conflict on their behalf) that there could be Union-supported consequences in Ireland if Britain intervened (most of the brigade's membership were known Irish revolutionaries), and 2) It served to solidify Irish support for the Union. . 3) It solidified the support of the Catholic minority for the Union cause.