The charge comes from The Lord of the Rings: The Return of the King from 2003, where King Théoden leads the riders of Rohan to aid Gondor at Minas Tirith. The horn signal and massed cavalry became one of the trilogy's most quoted battle moments, later clipped for gaming videos, sports edits and reaction memes. Its mix of a mournful horn, shouting riders and thundering hooves made it a shorthand online for impossible odds suddenly turning in your favour, which is why creators still reuse it for heroic reinforcements.