A plunderer and raider, he operated along the lawless Anglo-Scottish Border in the early 16th century, before England and Scotland were joined by the Union of the Crowns.
The romanticised picture of Armstrong was promoted by the nineteenth-century writings of Sir Walter Scott and Herbert Maxwell.
He burnt Netherby in Cumberland in 1527, in return for which William Dacre, 3rd Baron Dacre burnt him out at Canonbie in 1528; and Gavin Dunbar, the Archbishop of Glasgow as well as Chancellor of Scotland, intervened with an excommunication for Armstrong, whose activities made the central authority look weak and were a hindrance to diplomacy with England.
After his encounter with Johnnie Armstrong, James returned to Peebles, and spent a few days hunting at Cramalt Tower.
The variants sometimes open with a lament that it is not safe to appear before the king, or end with a thanksgiving that, as a reiver, Johnnie Armstrong had kept the English out of Scotland.
"The Ballad of Johnny Armstrong" has been recorded by David Wilkie and Cowboy Celtic, and by Gunning and Cormier.