Together with "Yoda's Theme", "The Imperial March" was premiered on April 29, 1980, three weeks before the opening of the film, on the occasion of John Williams' first concert as official conductor-in-residence of the Boston Pops Orchestra.
It is also played during Darth Sidious's arrival on the Death Star in Return of the Jedi, though it does segue into the Emperor's own theme as he appears.
Its major opening occurs as Imperial-class Star Destroyers amass and Darth Vader is first presented in the film, 19 minutes into the movie.
It is also heard softly at the end of the final credit roll, where it fades into the character's signature breathing, showing that the rest of the prequel trilogy will reveal how Anakin became Darth Vader.
It is played most prominently and recognizably during the final sequence when clone troopers assemble and depart Coruscant, foreshadowing the end of the Republic.
"The Imperial March" is quoted when clone troopers find dead Wookiees on Kashyyyk and when Padmé confronts Anakin on Mustafar.
In the 2015 Star Wars: The Force Awakens, two bars from the brass motif of "The Imperial March" are played after antagonist Kylo Ren regards the charred remains of Darth Vader's helmet, vowing to finally succeed where the Galactic Empire failed.
The theme can be heard once more when Vader attacks the Rebel soldiers trapped in a hallway; it is slowed down enough not to be obvious and joined with a chorus reminiscent of that from Revenge of the Sith.
For example, in episode 62, "Citadel Rescue", Anakin and Captain Wilhuff Tarkin both mention during their escape their good relationship with the Supreme Chancellor Palpatine.