As we saw at the outset of this section, Boden’s mate need not occur on the queenside; it also can arise against a king castled on the kingside or—as here—not castled at all. The point is just that the bishops need elbow room to be able to attack the king from two angles. Here the first clue to spot is the telltale attack by White’s a3 bishop against the diagonal running past Black’s king. The king has nowhere it can go; so if an attack along the h5-e8 diagonal could be added, White might mate. There's a pawn in the way on f7, but it can be cleared in the usual fashion by taking the pawn it protects with a threat and sacrifice: 1. Qxe6+, and now f7xQ is forced; then White mates with Bg6.

This position illustrates the value of castling. As we have seen countless times, a mating attack on the castled king generally requires one of the pawns in front of the king to have stepped forward (unless it is a back rank mate, but that's another story). But when your king is uncastled the pawn in front of it and the pawn on the next file—the d-pawn and the e-pawn—routinely will have stepped forward because that is the most natural way for your bishops to enter the game. So a failure to castle means your opponent is likely to have open diagonals leading toward your king, at least until it moves. There are other reasons to castle, too—principally that it brings your rook into the game; and occasionally the board will present such irresistible opportunities early that castling is best postponed or skipped. But in the most games, castling during your first eight moves or so is the best policy. (In this case Black’s lack of a dark-squared bishop hurts, too.)