This site now hosts a complete archive of PDF versions of The Problemist Supplement, from 1992 to the current year. This magazine is aimed mainly at newcomers to chess composition, so it is recommended for those who want to find out more about chess problems. You can find the archive here.
This week, we return to the orthodox direct mate threemover, with an outstanding
example selected by the late Robin Matthews, for his threemover chapter in Chess
Problems: Introduction to an Art, a book published 50 years ago this year. The theme
is white and black correction; no other clues!
The problem combines white and black correction. After the key 1.Qg7 (no threat)
randomly lifting the S from e4 allows 2...Kc5 3.Qg1 but fails to 2...Be4. Attempted
corrections which provide for 2...Be4 with 3.Qxc7 fail because of self-interference,
namely 2.Sc3+ Kc5! (3.Qg1?) and 2.Sf6+Kxd6! (3.Sd7?) . Moves of the black B
however, allow one or the other. After 1...Bb1 or 1...Bd3 2.Sc3+ leads to 2...Kc5 2.Sxa4,
while 1...Bd1 is met by 2.Sf6+ Kxd6 3.Sd7. Black can correct by playing 1...Bb3, which
maintains the guards of a4 and the sixth rank, but now the interposition is a
selfblock at d5, which allows White to play his random move. It turns out that
because of the need to keep lines open 2.Sc5+ is the only ‘random move’ available,
and there follows 2...Kxc5 3.Qg1 or 2...Bd5 3.Qxc7. Other lines are 1...Bxe4 2.Bxe4+
Kc5/Kb6 3.Qg1/Qxc7, 1...Kd5 2.Rh5+ Kc6/Ke6 3.Qxc7/Qe7 and 1...S any 2.Qxc7+ Kd5 3.Qc5.
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