Chess

TRY THIS miniature problem: composed by H Lange in 1937, it is White to play and mate in four.

The first thing you should notice is that 1.Kg4 is stalemate. The next thing to spot is that if it were Black's move, then he would be mated at once: 1...Kf5 2.Bh7 or 1...Kh5 2.Bf7. So all White has to do is preserve the status quo.

A quick look, however, confirms that it is impossible. The bishop on f6 cannot move without losing control of g7 or g5; the pawn on d5 cannot advance without giving up control of e6, so 1.d6 Kf5 spoils the mate White had ready; and 1.Be6 Kh7 leaves the black king impossible to trap in time.

So if White cannot preserve the status quo, he must re-create it. Here's the answer: 1.Kg2!! Kf5 (or 1...Kh5 2.Kh3 Kg6 3.Kg3) 2.Kf3 Kg6 3.Kg3! and mate next move.