Tuesday, April 01, 2008

Line Openings (1)

We open a line to allow a piece pass through it, a piece from those we call linear, that is those moving on a straight line (rook, bishop, queen, even the pawn when it makes its first move with double step). There are various ways for the opening of a line (or line-clearance).

Theme Bristol line-clearance : There is a parasitic white piece that moves towards a direction to open a line. A second white linear piece that gives or threats mate moves on the same line towards the same direction. The parasitic piece does not take part in the mating net.

The theme took the name “Bristol”, because it first appeared in a problem tourney at the city Bristol in southwest England. Please notice that this chess problems composition contest took place in the year 1861 (!).

(Problem 17)
Frank Healey,
First Prize, "Bristol Problem Tourney", 1861
White plays and mates in 3 moves
#3 (12+7)

The key move is impressive!
Key: 1.Rh1!
The rook moves in the first row to the right, to make space for the queen Qg6. The queen will move to square b1, and then it will move on the first row to the right, and it will give mate from the square g1.
Note that if the black knight Sb7 moves, there is an instant mate with Qd6.
2.Qb1 [3.Qb4#]
2...Bb5 (to allow black king escape by taking Sb6)
In the final mate, Rh1 does not take part, and that is the reason we call it parasitic piece).

Clarifications about the presence of some pieces:
(1) The parasitic piece in the problem-17 (by Healy) is Rd1.
(2) The bishop Ba1 was put there to inhibit a second solution, having key [1.Ra1!]. The second solution would render the problem useless.
(3) If, instead of putting a rook on f3, the composer had put a white pawn on f3 to hold the black pawn f4, then other solutions would arise, (Key 1.Sc8 [2.Qb6+ Kxd5 3.Se7#]), and (Key 1.Sa8 [2.Qb6+ 3.Sc7#]).

Theme black-Bristol : It is like theme Bristol, only with black pieces.
Theme bicoloured-Bristol : It is like theme Bristol, but the pieces have two colours.
Theme anti-Bristol : It is like theme Bristol, but the first piece prevents the second piece from reaching a critical square.

In problem-17, we saw the clearance of a row. Let us see another problem with Bristol line-clearance, where the diagonal line a1-h8 is opened.

(Problem 18)
Murray Marble,
White plays and mates in 3 moves
#3 (5+2)

There is only one variation, and that makes the problem rather easy to solve.
Key: 1.Ba1! Kxg2
2.h8=Q Kf2
In the mating picture the bishop is not taking any part, supporting or blocking, thus it is a parasitic piece.

You may read an essay by Milan R. Vukcevich here, where he presents, with many examples of problems of various types, the beauty of the Bristol theme.
Vuksevich mentions there that he was greatly influenced by his tutor Triantafyllos Siaperas.

(Update 26/02/2008) : We thank the International Master Harry Fougiaxis for his note that there was an inaccuracy on the definition of the anti-Bristol theme. He gave the following link for more details : page of Christian Poisson about themes.

[This post in Greek language].

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