The king is fighting like a madman on foot, Act V, scene vii
Scene summary: The two armies fight a pitched battle. Catesby appears on stage and calls to Richard’s ally Norfolk, asking for help for Richard. Catesby reports that the king’s horse has been killed and that the king is fighting like a madman on foot, challenging everyone he sees in the field as he attempts to track down Richmond himself.
Richard himself now appears, calling out for a horse. But he refuses Catesby’s offer of help, saying that he has prepared himself to face the fortunes of battle and will not run from them now. He also says that Richmond seems to have filled the field with decoys—that is, common soldiers dressed like Richmond—of whom Richard has already killed five. He departs, seeking Richmond.
Link to the information source: SparkNotes, "Richard III" - http://www.sparknotes.com/shakespeare/richardiii/section14.rhtml
Image Source: Circulating Collection, Print and Picture Collection, Free Library of Philadelphia. Subject: King Richard III – Shakespeare.
Original source: Shakespeare’s England by the editors of Horizon magazine. New York: American Heritage, 1964. p.45