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In the Stocchi block theme, named after the great Italian composer
Ottavio Stocchi, at least three selfblocks on a flight square lead
to mates which are separated by dual avoidance. This neat example
is enhanced by the clever means by which the key piece is
restricted to one square. The result is a highly unified problem.
Solution: 1.Ba6 threatens 2.Rb5. If b4 was occupied
by a dummy piece which had no other ability than to block White
would have three mates, 2.Sa4, 2.Sd7 and 2.Qc6. Black's three
captures on b4 each contain effects which eliminate two of the
three mates, giving the variations 1...Sdxb4 2.Sa4, 1...Scxb4
2.Sd7 and 1...Rxb4 2.Qc6. Other variations are
1...Kxb4 2.Qc3 and 1...Sd4 2.Rc4. Tries by the key
piece fail because they prevent one of the thematic mates - 1.Ba4?
Sdxb4! (2.Sa4?). 1.Bc6? Rxb4! (2.Qc6?) and 1...Bd7? or 1.Be8?
Jacob Hoover: In this problem the b4 rook is threatened by no less than
four Black units: both knights, the rook, and the king. The key 1 Ba6!
threatens 2 Rb5. Now the capture of the rook spells immediate doom for
Black, no matter how it's captured.
Peter Niehoff points out that this combination of Stocchi blocks with
tries defeated by thematic defences has been called the Krim theme.
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