In 1862 a small army of Texans invaded New Mexico in order to win it for the Confederacy. Following the third day of the Battle of Glorieta Pass, the Texans realized their predicament: Here we are between two armies, one double ours and the other four times our number, 1,000 miles from home, not a wagon, not a dust of flour, not a pound of meat. While the Confederates had forced a Union retreat on the rocky, forested battlefield around Pigeon's Ranch,...