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Grimshaw
Peter's Problem World with FIDE Master of Chess
Composition
Peter Wong
New terms introduced here are also added to Peter's
Glossary of Chess Problem Terms.
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As a rule, good chess problems are required not only to be sound, but
to demonstrate a specific
theme or a combination of themes. The
appeal of a problem – the point of it, in fact – lies in these
rendered ideas, which may involve certain recurring motifs or unusual
effects.
This month we will focus on the Grimshaw, a theme named after a
19th-century composer who made the pioneering example.
In a
Grimshaw, two
pieces of the same color interfere with each other’s line of action,
by playing in turn to a square where the two lines intersect.
Problem 37, an
oft-quoted classic, shows three such pairs of reciprocal
interferences: |
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37. Lev Loshinsky
Tijdschrift v.d. K.N.S.B.
1930
Commended
    
   
 
  
Mate
in 2 |
The a8-bishop is guarding
against a rook mate on c6, while the a7-rook is preventing another rook
mate on e7. So if Black plays 1…Rb7, then 2.Rc6, and if
1…Bb7, then 2.Re7. Another Grimshaw occurs on g7,
1…Bg7 2.Qxf7 and 1…Rg7 2.Qe5. These mutual obstructions
between a rook and a bishop are called Rook-Grimshaws.
The less common Pawn-Grimshaw,
where a pawn and a bishop hinder each other, is also illustrated in this
problem, with 1…f6 2.Qe4 and 1…Bf6 2.Qg4 completing the
main variations. Note how a Pawn-Grimshaw is possible only when the
pawn is on its initial rank, where its double-step can be disrupted.
Examining the non-thematic
black moves, we find that all have
set mates provided as well,
e.g. 1…Rxc7 2.Nxc7, 1…Bxd4 2.Nxd4, and 1…f5 2.Qd6.
White has one
waiting move
that will leave all of these
variations
undisturbed, namely 1.Bb3! which solves the problem. |
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Problem 38 also
features three groups of Grimshaw interferences, but here they involve
only one pair of black pieces, whose thematic defences lead to
changed play
across three
phases.
As set in the diagram,
1…Rc3 allows 2.Ne5, and 1…Bc3 allows 2.Ne3. White has a
try, 1.Nf2?,
which controls d3 and threatens 2.Qb4. This try move abandons the set
knight mates, but the added guard on d3 enables White to substitute the
queen as the mating piece against the same defences: 1…Rc3 2.Qf4 and
1…Bc3 2.Qd3. Black defeats the try with 1…Rb3!
The
key 1.Be3! attacks c5 and threatens 2.Rb4. Now since the key-piece
controls d4 as well, the white queen is able to take advantage of the
interferences in another way, 1…Rc3 2.Qd4 and 1…Bc3 Qe2. By-play
is provided by the a3-rook: 1…Rb3 2.Rc5, 1…Rd3 2.Qb4, and
1…Rxe3 2.Nxe3. |
38. Mircea-Mihai Manolescu
Revista de Sah
1956
1st Prize
  
Mate in 2 |
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39. Miroslav Subotic
Die Schwalbe
1992
Mate in 2 |
In
Problem 39, a white Rook-Grimshaw is harmoniously combined with a
black Pawn-Grimshaw. The latter takes place on c6, giving the set
variations 1…Bc6 2.Bb4 and 1…c6 2.Rd3.
Currently, a knight mate on f7 is prevented only by the pin on the long
diagonal, so unpinning the knight as the first move seems plausible.
The try 1.Rc3? does this, but hampers the bishop mate on b4, and so
permits Black to escape with 1…Bc6! (a move which stops the threat of
2.Nf7 by removing the b5-bishop’s guard of d7). 1.Bc3? reciprocates the
interference, disabling the rook mate on d3, so that Black can refute
with 1…c6! Therefore, we see white Grimshaw tries defeated by black
Grimshaw defences.
The
correct way to free the knight is 1.Ka2!, after which the
defences on c6 are answered by the unobstructed rook and bishop mates,
as in the set play. One additional variation is 1…Bxe5 2.fxe5. |
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41. Mark Kirtley
The Problemist
1988
1st Hon. Mention
Helpmate in 2
2 solutions
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In
Problem 41, a black Grimshaw occurs as part of a more elaborate
manoeuvre. In one solution, the black bishop wants to un-guard e4 to
allow Re2 mate, and the e6-rook wants to be shifted to let the white
bishop control the f5
flight.
To
accomplish both tasks in time, Black plays the bishop over a critical
square, g6, which the rook then occupies for an interference: 1.Bh7
Bd8 2.Rg6 Re2.
In
the other solution, the e6-rook must un-guard d6 for Bc7 mate, and the
black bishop must move to enable d4 to be guarded by the white rook.
Again, only a critical move followed by an interference are capable of
achieving both ends: 1.Rh6 Rf2 2.Bg6 Bc7. This helpmate in
addition shows a rarely-seen idea – in both parts, each white move
imitates exactly, in length and direction, the previous black move.
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