Ruy Lopez Berlin Defense Hanging Piece Puzzle (Rated 839): Back Rank Mate — One-Move Finish

This puzzle is a classic back rank mate pattern in a middlegame setting. The key idea is that the enemy king has limited escape squares because its own pieces and pawns restrict flight, while a rook on an open file can deliver a decisive check. Even when the position looks materially balanced or complex, a single tactical shot can end the game immediately. In classical chess, recognizing these mating nets is a major practical skill.