When Margia Dean is released by the Apaches and taken to the soldier's camp her white top is soiled. The next morning her top is pristine white and stays white to the end of the movie.
After the gun trader is killed by the Apache trying to bring them a bundle of rifles there are two Apaches shot trying to get the rifles. One body is to the right of the gun trader and the other is to his left. When the trooper goes out to retrieve the rifles both of the Apaches are now lying to his left. The one that moved is on his stomach instead of on his back as he was after he was shot.
Despite the title and one mention of Cimarron Pass, there never is an ambush there, or anywhere else.
When the Sergeant fills his canteen at the waterhole he takes a large drink and then fails to refill the canteen as he leaves.
Early in the movie the soldiers arrive at the civilian's camp carrying the 36 repeating rifles. At that point the soldiers are still carrying and using their old carbine single shot rifles. It is only later that the soldiers distribute the repeating rifles for use. Being heavily outnumbered they should have abandoned and destroyed their old guns and armed up with the repeaters much sooner and not have burdened themselves with their old rifles on their walk.
During the first scene, a lone rider stops his horse, turns, and raises his rifle in the air twice to signal other riders. However, they all were behind a boulder and would not have been able to see the signal.
A soldier is shot in the back with an arrow, then turns around and is shot in the front with another arrow. As he turns, the guide wire for the second arrow is visible against his dark shirt.
(at around 1h 9 mins) When a takedown is performed, a shadow of a camera and camera operator can be seen on lower left corner.
When the rifles became too burdensome, they could have removed a few pieces rendering them useless to the Apaches until the cavalry could return and reassemble them. Veteran soldiers should have known that.
Note: The rifles were not army issue and had been recovered from a gun smuggler selling to the Apaches. The soldier party finally destroys the rifles which makes sense and they should have done that much earlier and saved themselves a lot of effort hauling the 36 rifles for miles.
Margia Dean's Spanish accent is unbelievably bad and there is no reason the Apaches would have released her to the soldiers.