Fought Along El Camino Real de Tierra Adentro NHT
Soon after the Civil War broke out, Confederate political and military leaders hatched a plan for Western conquest. They would raise a force in Texas, march up the Rio Grande (along El Camino Real de Tierra Adentro), take Santa Fe, turn northeast on the Santa Fe Trail, capture the federal supplies at Fort Union, head up to Colorado, capture the gold fields, and then turn west to take California. New Mexico, Utah, and Colorado were "giant recruiting grounds" for potential enlistees to the Southern cause. All three states had populations loyal to the Confederacy, and southern New Mexico had already effectively seceded from the government at Santa Fe and formed a separate territory extending all the way to California.
Need for supplies
War materials in New Mexico were rumored to be extensive-6,000-8,000 rifles and 25-30 cannon-and the morale of the federal troops guarding the territory was said to be abysmal. Capture of the southwest would mean more wealth for the Confederacy from the rich mines of Colorado. Slavery could be expanded-especially into fertile California-and Arizona could be used as a springboard to invade Mexico.