Old western set in a cavalry outpost in the desert -- lots of friction between the commander and his newest lieutenant [closed]

I once watched this movie on television. I think this was in the late 1980s. It was a western, in color, in English. Most of it was set in and around a U.S. Cavalry outpost somewhere in the deserts of the Southwest, sometime in the late Nineteenth Century (i.e. after the Civil War had already come and gone). The fact that most of it was set in just one place gave me the impression that it was filmed on a fairly low budget. My best guess is that the movie was probably at least a couple of decades old before I saw it -- say, from back in the 50s or 60s?

I didn't recognize any of the actors at that time. Which eliminates several possibilities, since I had seen plenty of other old Westerns before then. For instance, I'm absolutely certain that this was not one of the old movies that feature John Wayne dressed up as a cavalry officer. Likewise, I would have recognized Jimmy Stewart, Clint Eastwood, Henry Fonda, or Gary Cooper.

With that said, here's what I remember about the characters and plot:

1. The protagonist is a young lieutenant who has just been transferred to a small fort in the desert. I gathered he had never been this far west before -- he'd been an officer for a few years, but stationed back East where you had all the comforts of the big cities, and rarely heard a shot fired in anger. We see him arrive and report in to his commanding officer.

2. The post commander is a black-bearded captain whom, we gather, has had his career hit a dead end. For several years now, he has essentially been stranded out here in the middle of nowhere. The captain asks a few questions about the lieutenant's father -- it appears that he suspects, from the surname, that he might have known the lieutenant's father a long time ago. The captain is correct; the lieutenant confirms that his father is General (Whatever), who is still on active duty at War Department Headquarters, back in Washington. The captain does not appear to be thrilled by this fact, but does not explain his past history with the general. On subsequent occasions, however, he makes unkind remarks which suggest skepticism about whether the lieutenant really has what it takes to get things done out here in the Wild West.

3. With the protagonist's arrival, there is now a grand total of four commissioned officers assigned to this post. The captain and three lieutenants. It turns out that one of the other lieutenants is engaged to marry a beautiful young lady from back East. In due course, we learn that she and the protagonist had a passionate romance, years ago, but something went wrong and it all fell apart. The lady's current fiance is not aware of this fact.

4. There is some trouble brewing with the local Indians. I can't remember what tribe -- for instance, Apache, or Comanche, or whatever. I believe it is mentioned that the captain is under orders not to launch an attack against parties of Indian warriors. Either not at all, or not except under rigidly defined circumstances, meaning any attack will be carefully reviewed by his superiors afterwards. (This will be important later.)

5. Here's a scene that I remember especially well. One evening, around sunset, the lieutenant is just taking a walk around the grounds of the fort when he bumps into the captain doing the same thing. They talk politely for a moment, and then suddenly a rifle shot rings out! The captain turns and runs in the direction the shot probably came from. He vaults over a waist-high split-rail fence and continues several paces further into the desert before dropping down behind a slight rise in the ground. The lieutenant is following him all the way, and they end up crouched down, side by side, peering over the crest of that rise as they talk about what's going on. They both figure an Indian scout decided to try his luck at bagging an Army officer, but missed. The absence of follow-up shots suggests that the sniper may already have decided to stealthily retreat rather than risk staying in one place long enough for a bunch of cavalrymen to come riding out and catch him.

When the captain decides it's safe, he stands up and starts walking back toward the fence, accompanied by the lieutenant. This is when the dialogue goes along these lines (allowing for my imperfect memory of something I saw over a quarter-century ago). For the sake of argument, I'm going to pretend that the other two officers were named "Smith" and "Jones."

CAPTAIN: By the way, Lieutenant, are you aware that I could have you court-martialed for desertion? As commander of this post, I have the authority to take myself out beyond the perimeter at any time. You, however, do not have that privilege. You left the post without permission.

LIEUTENANT: You are wrong, Captain! Regulations state that whenever the commanding officer goes outside the perimeter, he temporarily relinquishes command to the next senior officer! Lieutenant Smith is away on patrol, and my date of rank precedes Lieutenant Jones's by six weeks! So when you went over the fence, you left me in charge! As the acting post commander, I then exercised my authority by following you over the fence! Strictly by the book, Captain!

At this point, the captain suddenly shuts up, instead of expressing any agreement or disagreement with that line of argument. The implication is that he has realized the lieutenant is on solid ground, legally speaking, and there's nothing more to say about it without sounding like a fool. (I was hoping the captain had been joking, frankly -- I thought it would be idiotic for him to go in front of a military court and say, "I can't stand it when one of my subordinates follows me towards the source of enemy fire during the heat of battle. Punish him!" If I were a member of the court, I'd be highly sympathetic to the lieutenant's probable defense that he'd felt the captain's actions qualified as an implicit order to tag along and help fight the enemy . . . regardless of who was or wasn't the "senior officer still within the perimeter" at that very moment.)

6. At some point, the happily-engaged-to-be-married lieutenant opens a door and sees the protagonist is hugging and kissing the girl, and he is very upset when he asks her to assure him this kiss was done without her consent, and she can't bring herself to lie by agreeing. Shortly afterwards, this unhappy fiance is sent out into the desert in command of a cavalry patrol. This other lieutenant and his men never make it back alive. We don't know what happened to them until the captain (accompanied by the protagonist) takes most of his remaining cavalrymen out in search of the lost patrol, and finds their bodies. Ran into an Indian ambush, obviously.

7. Of course there's a final battle between the cavalry and the Indians in question. The cavalrymen win. (The captain had set it up so that the lieutenant and a squad of men appeared to be making camp alone, then the Indians attacked, hoping to overwhelm this small detachment quickly, then the captain and the rest of his cavalry counterattacked and turned things around.)

8. After the shooting is over, the captain has another conversation with the lieutenant. First he explains that moving to reinforce the lieutenant's position when it was under attack did not qualify as "launching an attack against the local Indians" according to the orders the captain is currently laboring under. For some reason, this is highly important. He also says to the lieutenant something along these lines: "Whatever you do, Lieutenant, never try to make excuses for your own mistakes. I remember a young captain who once tried to offer such excuses to a general. He will die, or retire, a captain." (I'm not sure if he said in so many words that the general had been our young protagonist's father, but it was clear that this was how the captain's career had hit a dead end.)

I've never run across that movie again. Any suggestions?