Red Sky at Morning — John D. McLaughlin

This action-packed story about an Old West group of lawmen, the Arizona Rangers, is set in the Arizona Territory of 1906-09. Murderers have fled to Mexico; miners have revolted in Cananea, Mexico. American citizens have been murdered and threatened. Ruthless, brutal smugglers are running guns across the border into Mexico to sell to the Yaqui Indians, and they will stop at nothing-- Young Joaquin Campbell has become an experienced Ranger. Elliott, his old friend and mentor, has resigned from the Rangers only to be called back repeatedly as his deadly skills as a gunman and his leadership ablilty is sorely needed.