The Army of New Mexico, also known as Sibley's Brigade, operated in Confederate Arizona and New Mexico territory between 1861 and 1862 before troops were moved to Louisiana. After the First Battle of Mesilla in 1861 the Confederate Territory of Arizona had been established, however many area forts were still in Union hands. The Army of New Mexico was tasked with taking these forts, moving into the New Mexico Territory moving into Colorado and California to control the gold and silver mines there to help finance the Confederacy.

The Army of New Mexico was originally formed in eastern Texas, where it trained at El Paso before being sent into New Mexico to Fort Thorn and then sent out to take Fort Craig from the Union. After a battle in which the Confederates captured four cannons, but lost many of its horses, they gave up taking the strongly defended fort and moved north. Due to the loss of the horses they were forced to dismount and abandon their supply wagons.

While moving north Sibley captured Albuquerque and Santa Fe. The Confederates engaged the Union at Glorieta Pass, where the Union were able to destroy their supplies and force them back to Albuquerque. The Confederates continued their retreat as Union forces followed. A small party of Confederates moving northwest out of Tucson skirmished with Union forces around Stanwix Station, this engagement is often considered the westernmost engagement of the Civil War. Eventually the remaining Confederate troops in Arizona and New Mexico were moved to Louisiana.

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