thereby creating an impregnable fortress. The attacker should generally put his pawns on squares of the opposite color as his bishop to prevent a blockade. Bishop and pawn versus bishop The attacker's bishop is practically useless and the defender can normally draw if his king can reach any square in front of the pawn that is not of the color of the attacking bishop; or if his bishop can permanently attack any square in front of the pawn. These endings are trivially drawn 99% of the time. Bishop and two pawns versus a bishop About half of these positions are drawn. In most other endings, a two pawn advantage is usually an easy win. For comparison, if the bishops were on the same color, 90% of the positions would be wins. There are three general cases, depending on the two pawns. In most endings, a pair of connected pawns have the best winning chances, but in these endings, a widely separated pair of pawns have the best chances unless one of the pawns is the wrong rook pawn. Doubled pawns With doubled pawns the position is a draw if the defending king can reach any square in front of the pawns that is not of the color of the attacker's bishop. The second pawn on the is of no help, so this is like the ending with only one pawn. If the defending king and bishop cannot accomplish this, the first pawn will win the defending bishop and the second one will promote. Isolated pawns With isolated pawns (on non-adjacent files), the outcome depends on how widely separated the pawns are. The more widely separated they are, the better the winning chances. The rule that holds in most cases is that if only one file separates the pawns the game is a draw, otherwise the attacker wins. The reason is that if the pawns are more widely separated, the defending king must block one pawn while his bishop blocks the other pawn. Then the attacking king can support the pawn blocked by the bishop and win the piece. If only one file is between the pawns, the defender can stop the advance of the pawns. See the diagram. If three files separate the pawns, the pawns normally win. However, there are positions where the defender can set up a blockade, especially if one of the pawns is the wrong rook