Last week’s defensive puzzle was taken from the Winning Moves feature in the August 2021 issue of CHESS.
In the game White lost after 1. Qd2 Re4 2. Nc3 Rdxd4, but he could have defended successfully by playing 1. Kf1! because 1… Rxe2? 2. Nc6+! bxc6 3. Rxd8+ Kb7 4. Bc8+ Ka8 5. Ba6+ wins. 1… c5 probably has to be tried instead, but Black shouldn’t have enough for the piece.
Congratulations to everyone who found Kf1.