A mounted British patrol manned by Irishmen (this being right before The Irish Revolution) is off on a mission in Mesopotamia during The Great War. Right after the opening credits, the patrol's only officer, a lieutenant, is shot off his horse and killed. Because said lieutenant was also the only one who knew what their mission was, the sergeant (McLaglen), who is now in charge of the 12-man patrol, is at a loss for how to proceed. He elects to head across the desert, making for the river, where the main army is supposed to be. It's a Thirsty Desert, so his men are pretty happy when they find an oasis that has both water, food in the form of date trees, and shelter in the form of an abandoned mosque. But when the unseen Arab enemy that is stalking their patrol makes off with their horses during the night, the oasis becomes a trap, and the men of the patrol are stuck in a grim and hopeless battle with an invisible enemy.
- Absence Makes the Heart Go Yonder: Herbert tells his fellow troopers that his wife delivered a boy, Herbert Jr., who is now two months old. The unit has been in Mesopotamia for over a year. Herbert has not figured this out.
- Big Damn Heroes: After a heat-addled Abelson wanders out into the desert and gets shot, Morelli charges out into the Arab sniper fire, retrieves him, and brings him back.
- Chromosome Casting: No women.
- Dead Guy on Display: Desperate for relief, the sergeant sends Jock and Matlow off on foot, carrying all but two of their water bottles. Some time thereafter, the men return—dead, tied to two of the patrol's horses by rope, and apparently horribly mutilated.
- Death by Childbirth: The sergeant tells Morelli that he was once married and his wife died in childbirth. The sergeant hated the boy at first but grew to love him, and is now worried about what's going to happen to his son now that he's doomed to die in the desert.
- Department of Redundancy Department: One of the troopers, named Herbert Hale, has named his son "Herbert Hale Jr. the 2nd."
- Dressing to Die: The sergeant has been stripped to the waist, as one might expect for a soldier in the Mesopotamian desert. But when he's the only one left, he puts on his full uniform.
- Dwindling Party: The patrol—12 men and 1 officer—is gradually picked off one at a time by the Arabs. The sergeant is the only one left when relief arrives.
- Fatal Family Photo: Hubert shows the others pictures of his wife. He's picked off not long after. Possibly subverted in that everyone is getting picked off.
- The Film of the Book: Based on the 1927 novel Patrol by English author Philip MacDonald.
- The Fundamentalist: Sanders (Boris Karloff), who is religious to the extreme. He urges the other men to save their souls before they're killed by the Arabs, and he yells at one soldier when said soldier is telling tales of his sexual exploits with Malay native girls. Eventually, he completely snaps, dressing up in a sort of John the Baptist outfit and approaching the Arabs with a cross. He's shot for his trouble.
- Gentlemen Rankers: Pearson is from the upper crust and could have gotten a commission, but he tells the sergeant that he wanted to earn it, so he signed up for the ranks.
- Hope Spot: The patrol has been reduced to its last three men—the sergeant, Morelli, and Sanders (who has cracked and been tied up)—when they are spotted by a British patrol plane. The sergeant and Morelli are giddy with relief, until they see that the pilot is landing outside their perimeter. The pilot gets out of his plane and is immediately shot In the Back by the Arabs.
- Impairment Shot: Ableson, standing watch on the edge of the perimeter, is suffering from the heat. The film shows a shot of the dunes shimmering and distorting.
- Improbable Aiming Skills: The Arabs hate to waste bullets - usually whenever one of the patrol is not actually behind cover, only one shot is fired - which invariably kills the target.
- I Take Offense to That Last OneSoldier: You were troop sergeant major, but you had been broken for being drunk and disorderly, for setting fire to your tent, and appearing on the parade ground with nothing on but your drawers and your Toby.
Other soldier: That's a dirty lie. I did not set fire to my tent.
- New Meat: Pearson, the fresh-faced and hopelessly naive boy who joined up because he wanted adventure out of Kipling. Not surprisingly, he's the first of the enlisted men to be killed.
- No Name Given: McLaglen's character is only ever referred to as "Sergeant".
- Nothing Is Scarier: Throughout the movie, the Arabs are killing the men of the patrol one at a time, but they are never seen. They don't pop up until the end, when the sergeant is playing dead. Even then, they're The Faceless, wrapped up in robes and face masks.
- Playing Possum: How the sergeant takes out the Arabs at the end. He charges out, sets fire to the plane, and removes its machine gun. He then runs back to the oasis and plays dead. As the Arabs finally rise out of their hiding places in the desert and approach, the sergeant whips out the machine gun and massacres them.
- The Siege: A particularly grim small-scale version, as the men of the patrol are trapped inside the oasis, being picked off one at a time by the Arabs surrounding them outside.
- Sole Survivor: The sergeant is the only one left when a British regiment, attracted by the fire he set, arrives. When asked where his men are, the sergeant just points to the graves.
- Thirsty Desert: Played straight at first, with the patrol seeming to be in pretty desperate straits as they wander through the desert, but surprisingly averted afterwards when they find an oasis with more than enough water. After that, they have different problems.
- Tightrope Walking: Morelli and his common law wife did this in a circus act before he enlisted. One day the wire broke, and she died in the fall.
- Video Credits: At the beginning of the film.
- War Is Hell: A particularly effective use of this trope, as a random patrol suffers and dies in a place they should not be for a war they have no interest in against an enemy they can't even see.
- What Happened to the Mouse?: Brown disappears during the night, leaving a note behind in which he tells the sergeant that he's going to sneak around the perimeter and kill a couple of Arabs in revenge for Jock and Matlow. He is never seen again.