Deflection and overload: a common chess weakness

A defender is doing two jobs at once. Lean on it.

Their piece is the only thing defending two things. Attack one, the other falls. Or one piece is overloaded: tied down to too many duties. Lean on it.

• vs game: a knight defended both a hanging bishop and the back rank. Attack the bishop, the knight has to move, the back rank falls to mate.
• vs puzzle: a queen tied to defending mate AND a piece. Take the piece, the queen has to recapture, mate next.