Even though the arrogance of medieval knights sometimes worked against them, more often than not they proved an asset in battle during most of the High Middle Ages. Nevertheless, by the inal years of that era, historian Robert Jones points out, their military efectiveness and at times dominance over infantry ďhad vanished from the battleield.Ē21 One reason for this dramatic development was that cavalry armor and weapons became more and more expensive. Eventually, as national governments increasingly switched from militia to standing armies, the costs of maintaining large units of knights became unafordable. Another reason for the demise of medieval cavalry was that infantry became increasingly strong in the periodís last century and a half. Still another factor was the development of irearms in those same years. Cannonballs and bullets ired by hand-held guns rendered even the heaviest armor useless to those horsemen who were unfortunate enough to be hit by them. Military strategists saw that the wisest approach was to eliminate most of a cavalrymanís armor, along with the lance, and give him a gun. In this way, medieval cavalry transitioned into early modern cavalry, and thereafter traditional European knights existed only in history books, novels, and movies.