After capturing Confederate Arizona's western outpost, Carleton prepared to march east with his main body in July, intending to enter New Mexico through Apache Pass in southeast Arizona. To prepare for the advance of his main force, he sent a column ahead as he had on his march from Yuma to Tucson. The column was led by Capt. Thomas L. Roberts of Company E, 1st California Infantry, accompanied by two 12-pounder mountain howitzers under the command of Sgt. James D. Monihon, a 22-man cavalry escort from Company B, 2nd Regiment California Volunteer Cavalry, led by Capt. John C. Cremony and 21 wagons plus 242 mules and horses.