Bishops of opposite color endings are notoriously drawish, even where one side has one or two extra pawns. Some common drawing plans are demonstrated in the positions below.
Even where the stronger side has two connected passed pawns, this is not enough for a win in this ending provided (1) the pawns have not yet reached the sixth rank and (2) the defending king is able to get in front of the pawns. The blockading procedure is demonstrated in the following diagram:
When on the pawns is a knight’s pawn, the following technique of controlling the queening square with the bishop while the king blockades the other pawn is key to holding back the advance.
Typically, the further apart the pawns are, the more drawish the position becomes, particularly where one of the pawns is farther advanced than the other such that they can be controlled along the same diagonal, such as this:
However, it should be noted that a central pawn and a rook pawn win, as in the following diagram, where the stronger side is able to outflank the weaker side’s king with no fewer than 4 Zugwang moves!
Sometimes, the number of pawns on the board is irrelevant, as the weaker side can easily defend by erecting an impenetrable fortress. Fortresses are a key concept in these endings, and the weaker side should always be thinking about how to create one.
In the following position, Bacrot resigned. However, it is a dead draw… for instance
As most of our readers will remember, a crucial game in the last World Championship between Anand and Topalov featured a tense bishop of opposite colors ending, in which Anand could have held on and drawn, though missed the key idea and allowed for white to achieve the uncommon outcome of winning a bishop of opposite color ending. This game is worth looking over again and again, as it is (1) very instructive and (2) demonstrates a fantastic winning plan in such a position by Topalov. I recommend watching Kingscrusher’s video on the game below, his explanation of the position is impeccable, as always.