This is the famous Paul Morphy chess puzzle, rumored to have been composed by Morphy when he was just 10 years old!
White to play and mate in two moves.
Click to show solution
- Ra6!
If 1. … bxa6, then 2. b7#
If black moves the bishop anywhere, then 2. Rxa7#
This is the only solution, because white needs to prevent black from playing pushing the pawn to a6.