 Company A left Tucson on May 14, leaving behind a small detachment under the command of Lieutenant James Henry Tevis to watch for the approach of Union forces.Unknown to the Confederates, on that same day, the Union California Column finally left its bivouac at the Pima Villages for its final advance on Tucson.On May 15, Colonel West and his advance California detachment moved out of the Pima Villages for Tucson, going through Rattlesnake Springs to old Fort Breckenridge, and camped that night in the "Canyon de Oro".