No love for Windtalkers (2002)?
The Guns of Fort Petticoat (1957) is pretty good, mainly thanks to Audie Murphy’s experience with drilling raw Texas National Guard recruits. Murphy’s character, a fictional lieutenant serving under Col. John Chivington, recognizes the harm that attacking the settlement at Sand Creek would do and goes AWOL to warn his hometown of reprisal from the natives. Virtually all of the men in the Texas town are off fighting the Civil War and the women they left behind are highly suspicious of Lt. Hewitt, due to his joining the US Calvary instead of the rebels. After one of the women turns up as being killed in a Cheyenne raid, Hewitt convinces the rest of the women to hole up in a nearby mission and drills them in defending themselves.
Of course, the film takes some liberties with the real history, notably Chivington’s fate.