“Things are looking bleak for our heroes: they gave it their best, and may have even briefly looked like winning, but in the end, the villains were too strong, the heroes too few, and all that’s left is just enough time for some last words and a Last Stand…
“…Wait, what’s that? Did I just hear a bugle?
“It’s the Cavalry, riding in to save the day! Maybe they’re some minor characters who’ve banded together to mount a rescue, or maybe they’re the local Men of Sherwood, or maybe they are characters Not Quite Dead after all, or maybe they’re Han Solo diving into the fray at the last minute. Any way you slice it they exist to storm in at the last minute, save the heroes and convert a Downer Ending into an out-and-out win for the good guys.
“This and other related tropes are named for the classic Western trope of the US cavalry charging over the brow of the hill just in time to save the beleaguered settlers from the Indians in far too many Westerns to count.” — from “The Cavalry,” www.tvtropes.org.
In this instance, the U.S. Cavalry arrives around the 1:30 mark. (Posted nearly three years by LatestSightings.com.)
Bill Murray in Mad Dog and Glory (1:20 mark): “The Seventh Cavalry. What’s that make us, the friggin’ Comanches? Dut-dah-dut-dah-dut-dah-dut-dah-TAT-tuh-TAT-tuh-dahhh!”