The Saint Patrick's Battalion (), formed and led by Jon Riley, was a unit of 175 to several hundred immigrants (accounts vary) and expatriates of European descent who fought as part of the Mexican Army against the United States in the Mexican-American War of 1846 to 1848. Most of the battalion's members had deserted or defected from the U.S. Army. Made up primarily of ethnic Irish and German Catholic immigrants, the battalion included Canadians, English, French, Italians, Poles, Scots, Spaniards, Swiss, and native Mexicans, most of whom were Roman Catholics. Disenfranchised Americans were in the ranks, including escaped slaves from the American South. The Mexican government offered incentives to foreigners who would enlist in its army: granting them citizenship, paying higher wages than th