[MEHDI]

1 F. Healey, 1st Pr. Chess Monthly, 1885

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What should the first step be when the solver is confronted by a board full of pieces and no obvious mating idea in sight? The most sensible approach is to decide whether the key might put Black in zugzwang. If this is impossible then the key will have to carry a threat of mate in one. In most cases it is quite clear whether or not zugzwang is likely. Black may have several irrelevant moves which obviously cannot allow mate in one, in which case zugzwangis out of the question. This is not the case in Diagram
1, however, and if we look at Black's available moves we soon find the variations l...Ke5 2 Nd3, 1...N moves 2 Bg3, 1...B moves 2 Qxb8, 1...Qe5
2 Ne2, 1...Q elsewhere 2 Qd6 (or Q takes Q). Thus Black is already in zugzwang and White only needs a waiting move to solve the problem.
Some of the White pieces are fully employed in the above variations and moving one of these might disrupt the mates which are already arranged, so we have to look around for pieces irrelevant to the pre•
arranged mates. This narrows the choice down to the K on a3, B on g6 and R on a4. However, moving the B on g6 allows Black's g-pawn to move, while king moves run into trouble from pins and checks, for example,
1 Ka2/b3? Be6+, I Kb4? Nd5+ or 1 Kb2? Qe5!. Can the rook at a4 move without affecting the status quo? Certainly it cannot move along the fourth rank, for then Black has a check with his queen. Similarly a7 and a8 may be eliminated. a5 gives Black the move ...bxa5 so we are left with a6. This has no harmful effects so must be the key. 1 Ra6! is an even more mysterious rook move than Nimzowitsch's famous ...Re8! Looking back at Diagram I, a more experienced solver would suspect zugzwang even before he had begun to explore Black's possible moves. Every piece has a purpose in a problem and the function of White's bS pawn looks likely to be simply the prevention of the pass move ...b5. The immobilisation of the g7, h5 and e4 pawns by blockading pieces provides further evidence that the problem's construction is motivated by the necessity to prevent nondescript moves by Black.