It's been some time since I've posted any logic puzzles, and I don't remember ever posting a chess puzzle, so today I'll kill two birds with one stone. In fact, the following position represents two puzzles in one. (You don't have to be a grandmaster at chess to solve it, so even if you only know the basic rules of the game you should give it a try.)
The first part of the puzzle requires more logical thinking than chess skill. Explain how this highly unlikely position could possibly be reached in a game. You don't have to show all the moves, but you should be able to convince yourself that it is a legal position.
Second, it's white's turn to move. Show how white can checkmate black in at most four moves.
I'll give the answer and the original source of this puzzle in an upcoming post. (Update: the full solution is up.)
The diagram image is courtesy of the Online Chess Diagram Editor.