Henry Hopkins Sibley was born in Natchitoches, Louisiana in 1816. He spent his youth in Missouri, Ohio, and Louisiana. He graduated from the United States Military Academy in West Point in 1838. He served in the United States Army during the Second Seminole War, the Mexican War, and other Army postings.

He resigned his U.S. Army commission in May 1861, and then met with Confederate States of America President Jefferson Davis on a strategy to expand the CSA occupation in the Western United States. In 1862, he moved troops into the Territory of New Mexico and engaged with Union forces several times, most notably at the Battle of Valverde and the Battle of Glorieta Pass. After significant troop losses and supply line disruption, Sibley retreated to Texas.