There were also some significant differences between campaigns fought during the Civil War (1860ish through 1865-66) and those that came after mid-1866. Most of those came from the nature of the troops that were doing the fighting. The great majority of the campaigns in the Southwest during that period were conducted by Volunteer regiments (mostly from California), and they brought a different dynamic to the conflict. Although some of the senior leaders had Regular Army experience (James Carleton to name one example), the majority of the regimental and company officers were also volunteers and shared the motivations of their men to a great degree.

Volunteer units were, on the whole, more aggressive than their Regular counterparts and more likely to wage what Utley called an "exterminationist" style of warfare. Chivington's men are (of course) the ultimate example of this, but that mindset did exist to lesser degrees in units from California and New Mexico. Regular units tended to be less extreme, although some officers were more aggressive than others when it came to campaigning.

"To Cross the Deadly Ground" goes into tactics between the Civil War and the Spanish-American War, and does comment to a degree on the field tactics used by the Army. There was informal doctrine, mainly pushed out by officers through private publishers or articles in The Cavalry Journal (once it was established) or The Army and Navy Journal and Journal of the Military Service Institution. Don't forget that the Army didn't really have a strong education system at this time, either (it took the Little Bighorn to push most of that along, although both Sherman and Sheridan had recognized the need prior to that).