Boden's mate — two bishops crossed

Mate in 2 White to move · Mate with bishop and knight · Difficulty about Elo 1600

The plan

Two bishops on crossing diagonals trap a king that has castled queenside. The pattern is rare, but when it occurs it is lethal. The precondition: one bishop sweeps the long diagonal to the king, the other holds the squares on the other side. The only thing in the way is the defender's own pawn — and that pawn is FORCED to step aside. The queen captures with check in such a way that only this one pawn can recapture; in doing so it opens the diagonal to its own king with its own hand. The bishop moves in and every flight square is occupied: two by the defender's own pieces, the rest by the two bishops. Remember: where two bishops cross, a pawn move costs the king.

Why this level: You have to know the mating pattern to even consider the queen sacrifice; without a model you will hardly find it.

The solution, move by move

1. 1. Qxc6+ Not a material gain but a forcing measure: the pawn is meant to open the diagonal, and it may only do so by recapturing.
2. 1… bxc6 Forced. The king cannot sidestep, and nobody can block — its own knight stands on the wrong square for that.
3. 2. Ba6# The second bishop comes onto the diagonal that has just been opened. The defender blocks two flight squares himself.

More in Mate with bishop and knight

• Arabian mate — the oldest mating pattern Mate in 1
• Smothered mate — the king in its own prison Mate in 2