The New Mexico Campaign is a military operation of the Trans-Mississippi Theater of the American Civil War from February to April 1862 in which Confederate Brigadier General Henry Hopkins Sibley invades the northern New Mexico Territory in an attempt to gain control of the Southwest, including the gold fields of Colorado and the ports of California.

Historians regard this campaign as the most ambitious Confederate attempt to establish control of the American West and to open an additional theater in the war.

It is an important campaign in the war's Trans-Mississippi Theater, and one of the major events in the history of the New Mexico Territory in the American Civil War.

The Confederates advance north along the Rio Grande from Fort Bliss in Texas.

They win the Battle of Valverde but fail to capture Fort Craig or force the surrender of the main Union Army in the territory.

They continue north across the border towards Santa Fe and Fort Union, leaving that Union force in their rear.

At Glorieta Pass, the Confederates defeat another Union force from Fort Union, but are forced to retreat following the destruction of the wagon train containing most of their supplies.

Confederate success in this failed campaign would have denied the Union a major source of the gold and silver necessary to finance its war effort, and the Union navy would have had the additional difficulty of attempting to blockade several hundred miles of coastline in the Pacific.

A Confederate victory would have also diverted Union troops which, following the invasion, were used to fight native tribes on the plains and in the Rockies