The setting is British India, aka The Raj, on the northwest frontier, which later became Pakistan. The 41st Bengal Lancers are a crack regiment defending the frontier against mountain tribesmen. Lieutenant Alan McGregor (Cooper), a hot-headed but brave veteran officer, welcomes two new arrivals: Lt. Forsythe (Tone), a wisecracking Deadpan Snarker, and Lt. Stone (Cromwell), a newbie fresh out of the Sandhurst military academy. It just so happens that Lt. Stone is the only son of Col. Stone (Standing), the regimental commander. The colonel's devotion to the army made him a Disappeared Dad years ago; young Stone speculates that his father might not even know that his son went to Sandhurst.
Meanwhile, army intelligence has learned that native chieftain Mohammed Khan is organizing a campaign against the British, uniting the tribes for a major attack. The regiment must prevent an ammunition shipment from falling into the hands of the enemy, but Lt. Stone's inexperience winds up jeopardizing the mission.
- Affably Evil: Mohammad Khan, who seats his prisoners to a fancy gourmet dinner, and then politely asks what route the ammunition train is taking. When his British guests won't tell, he says "Come now gentlemen. Must I proceed to these absurd and unpleasant extremes?". Then he tortures the bejesus out of them with lit bamboo sticks.
- Artistic License Geography: The name of the film is The Lives of a Bengal Lancer, and Bengal was on the eastern side of the Raj (most of it became Bangladesh). But the Lancers are specifically described as being on the northwest frontier, which would later become Pakistan.
- Played straight with Douglas Dumbrille (Mohammad Khan).
- In-Universe Barrett dons blackface to infiltrate the enemy camp, as do McGregor and Forsythe when they attempt a rescue of Lt. Stone.
- Cold-Blooded Torture: McGregor and Forsythe are tortured via lit bamboo sticks stuck under their fingernails.
- Dead Guy on Display: Barrett, the officer who is sent into enemy territory disguised as a native, is sent back to the regimental camp as a corpse, tied upright to the saddle of his horse.
- Facial Dialogue: In the final scene, Colonel Stone and his son exchange a handshake and a brief look that says volumes more than they've managed to in the whole movie preceding it—namely, gratitude and So Proud of You.
- Heroic Sacrifice: Forsythe is about to make the mortally dangerous sprint to the ammunition dump when McGregor knocks him out with a punch to the face and does it himself. McGregor dies, but not before he succeeds in throwing the torch into the ammo tower and blowing everything up.
- Honey Trap: Mohammad Khan's sexy concubine, who uses her feminine charms to lure Lt. Stone out of camp, which allows the Muslims to kidnap him.
- I Need a Freaking Drink: Lt. Forsythe's playing of the pungi flute lures a cobra into the room, which McGregor has to shoot. A very shaky Forsythe then tries to pour himself a shot of whiskey but McGregor does it for him.McGregor: Allow me. You might spill it.
- Jerkass Has a Point: Col. Stone insults his son with a harsh dressing-down in which he says that the Indian frontier is no place for a new graduate from the academy. He's right, though: Lt. Stone's inexperience and naïveté makes it easy for Mohammad Khan to use a honey trap to lure Lt. Stone away.
- Killed Mid-Sentence: Played with. The Lancers are taking enemy fire from the rocks. McGregor wants to charge. His superior officer says "I'd like to have you with me in a war, but for peacetime you're—", and then is shot off his horse. But he's Not Quite Dead, and manages to gasp out "...too...too impetuous" before he croaks.
- Naïve Newcomer: Lt. Stone's arrival at army HQ allows for a little lecture, including a map, that explains where the 41st Lancers are stationed and what their job is.
- Married to the Job: Col. Stone says "the service comes first", but his wife didn't understand that, which is why he doesn't have a wife anymore and hasn't seen his son in years.
- Right-Hand Cat: The villain, Mohammad Khan, is introduced playing with kittens.
- Shut Up, Kirk!: After McGregor expresses outrage over Col. Stone's refusal to go rescue his son, Major Hamilton dresses him down, saying that devotion to duty above all things is necessary on the frontier and that Col. Stone can't play into Mohammad Khan's hands and expose the ammunition shipment, not even to save his son.
- Snake Charmer:
- A professional snake charmer does this in the Lancers' camp.
- Later, and to his horrified surprise, Lt. Forsythe accidentally lures a snake into his quarters by noodling on a pungi flute.
- Stiff Upper Lip: Col. Stone's main problem, in that he finds himself unable to express affection for his son. He looks wistfully at a picture of his wife and baby boy, but hides it away when Lt. Stone enters the office. After giving his son an insulting dressing-down and telling his son that he didn't send for him, Col. Stone hesitantly says "I'm very glad that—", but it's too late, as Lt. Stone has turned on his heel and left the room.
- We Have Ways of Making You Talk: Trope Maker, when Mohammed Khan is threatening the officers with torture. Also a case of Beam Me Up, Scotty!, as the actual line is "We have ways to make men talk."
- "Well Done, Son!" Guy: Lt. Stone, who hasn't seen his father in years, is desperate for the old man's affection and respect. When Col. Stone proves incapable of expressing it, his son is deeply hurt.
- White Man's Burden: Col. Stone's XO explains that Stone is the way he is because attention to duty above all else is the only way "a handful of men" can rule over 300 million natives. This being a film made in Hollywood in the 1930s, the justice of Britain's rule over India isn't even questioned.