Pyron was a major in the Confederate Army and in March 1862 commanded a Confederate force of 200-300 Texans on an advance expedition over the Glorieta Pass. The pass was a strategic location on the Santa Fe Trail at the southern tip of the Sangre de Cristo Mountains southeast of Santa Fe. Control of the pass would allow the Confederates to advance onto the High Plains and to make an assault on Fort Union, the Union stronghold along the invasion route northward over Raton Pass. After a few small battles, Union forces forced the withdrawal of the Confederates.