When a king is under direct attack by one (or possibly two) of the opponent's pieces, the player is said to be in check. When in check, only moves that remove the king from attack are permitted. The player must not make any move that would place his king in check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there are no moves that remove the king from attack.
Erregea aurkariaren pieza baten (edo agian biren) erasopean dagoenean, jokalaria xakean dagoela esaten dugu. Xakean dagoenean, erregea erasotik aldentzen duten mugimenduak bakarrik onartzen dira. Jokalariak ezin du erregea xakean utziko duen mugimendurik egin. Jokoaren helburua da aurkariari xake mate egitea; horretarako, aurkaria xakean utzi behar da, eta, gainera, erregea erasotik aldenduko duen mugimendurik ezin egiteko moduan.