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White is to play and mate in two moves. Have a go at solving this first and then, when
you are ready, click the button below to see the solution and a commentary explaining
what the problem is all about.
One particular feature of the diagram is the open position of the mirrored bK;
all eight adjacent squares are vacant. However, the squares on the 5th rank above the
bK may be occupied with interesting effect; 1...c5/Rd5/Re5 2.Qxd2/Qb4/Qxe5. Two tries
confirm the self-blocks discovered in the set play. 1.Re6? (>2.Qe5) 1...c5/Rd5/Rxe6
2.Qxd2/Qb4/Sxe6 but 1...Sc6! refutes. 1.Re3? (>2.Rd3) 1...c5/Rd5/Rxe3+ 2.Qxd2/Qb4/fxe3
but 1...Bf1! has no answer. White opening moves that cut the line of wRe1 will transform
elements of the set play. 1.Se4? (>2.Qc5) 1...Rd5/Re5/Rxe4 2.Qxa1/Qxd2/Rxe4. This try
fails to 1...Sa6! The mate following 1...Rd5 has been changed from 2.Qb4 to 2.Qxa1. Of
greater interest is the mate after 1....Re5, changed from 2.Qxe5 to 2.Qxd2. This latter
mate occurred after 1...c5 in the set play; 2.Qxd2 is said to be a transferred mate.
1.Se3! (>2.Sf5) 1...c5/Rd5/Re5 2.Qxa1/Qxd5/Qb4. It will be seen from this that
2.Qxa1/2.Qb4 are also transferred mates! It is of interest to determine the mechanism
by which these effects are engineered. 1.Se4? cuts a guard of e5 but adds one to c5
whereas 1.Se3! cuts a guard of e5 but adds one to d5. Thus there is an alteration of
control over the c5/d5/e5 squares. The by-play is completed by 1...Rxe3+/d1Q+/g3/Rf8
2.fxe3/Rxd1/Sf3/Se6. Controversially we also have 1...Rf7/Sd6/Se7 2.Qd5/Qd5/Se6.
Altogether 2.Se6# occurs twice and 2.Q(x)d5# three times! Defences giving rise to the
same mates are known as black duals and these are usually regarded as undesirable
repetitions. Here they could have been eliminated by the removal of bSc8 and the shift
of bRe8 to e7. The post-key play is already considerably richer than that following the
tries but presumably Zagoruiko valued the interferences supplied by bSc8.