Lev Polugaevsky (Black) Puzzle: Win — Discovered Attack
A discovered attack occurs when one piece moves away and uncovers a line attack from a rook, bishop, or queen. In this chess endgame, a seemingly direct attacking move also removes the blocker protecting a valuable target. The resulting double effect creates a decisive material gain. The key is to recognize that the moved piece does not need to attack the target itself; opening the file behind it can be even more powerful.