Kickball is among the earliest ball games in East Asia for which we have evidence, predating polo by a couple of centuries. Although less well known than polo to historians of sport, kickball was of equal importance for many centuries. The attribution of the invention of the game to high antiquity lacks credence, but there is ample historical evidence for its practice in China from the Warring States period (480–221 B.C.E.) onward. A similar game was played in Japan as early as the eleventh century, but its historical relationship to the Chinese version remains unclear. The versions of the sport played in the two countries overlap in certain respects, especially in their emphasis on keeping the ball in the air primarily through kicking, but there were differences in the type of ball used and in the style of play.