Events in the far West during the Civil War tend to barely have footnote status in most histories of that conflict. So it is with the battle of Apache Pass. On May 20, 1862, Union forces captured Tuscon in the Arizona territory from a small Confederate garrison. Colonel James H. Carleton, in command of the Union troops, intended to march into New Mexico. To prepare the way for the main force, he sent a column ahead under Captain Thomas L. Roberts of Company E, 1st California Infantry. Roberts had under his command 116 infantry, twenty-two cavalry and two mountain howitzers that would come in very handy.
Traveling through Apache Pass on July 15, the Union column was attacked by about 500 Chiricahua Apache warriors under Mangas Colorado and Cochise. The Apaches had picked a good location to fight. They controlled the Apache Pass springs, and the Union troops were low on water and tired from their march. The Union attack made no headway against the Apache warriors firing behind boulders and trees. Roberts retreated to the mouth of the Pass, unlimbered the two mountain howitzers and began to advance again.
The mountain howitzers turned the tide of battle, with the Apaches retreating after dark., with thirsty Union troops taking the springs. Union losses were two men killed and three wounded. Apache dead were sixty-six, almost all due to fire from the mountain howitzers, a weapon that the Apaches had no counter to.