Lesson
White to move. Main line: 1. Qe7#
Qe7 is mate because the queen checks the king from the neighboring square and the bishop on h4 protects the queen along the h4–g5–f6–e7 diagonal. Black cannot capture the checking piece, interpose against a contact check, or move the king to safety.
The important feature is Black’s self-made cage. The rooks on d8 and f8 occupy two flight squares, while the pawns on d7 and f7 occupy the other two. Pieces that normally defend a king can become walls when there is no room behind them.
Use a three-part scan in similar positions: identify every legal king move, ask whether the checking piece can be captured, and ask whether the check can be blocked. Only after all three answers fail should the move receive the mate sign.