Brian Boru's March
Brian Boru's March is a traditional Irish tune.
Brian Boru was a High [King of Ireland] who founded the O'Brien dynasty.
In 1842, a version of the song was published by Dublin [Monthly Magazine]. In 1969, the song was recorded by The Chieftains.
Horslips used it in 1976, as the intro and basis for "Trouble " from the album The [Book of Invasions (album)|The Book of Invasions].