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Grimshaw (chess) A. G. Corrias, Good Companion, 1917
White to play and mate in two
A Grimshaw is a device found in chess problems in which two pieces (usually a rook and bishop) arriving on a particular square mutually interfere with each other. It is named after the 19th-century problem composer Walter Grimshaw. The Grimshaw is one of the most common devices found in directmates. Examples with descriptionThe theme can be understood by reference to the displayed example by A. G. Corrias (published in Good Companion, 1917). A. G. Corrias exampleThe problem is a mate in two (White must move first and checkmate Black in two moves against any defense). The key is 1.Qb1, which threatens 2.Qb7#. Black has three ways to defend against this.
It is the other two black defenses, however, which show the Grimshaw theme.
It is this mutual interference between two black pieces on the one square (in this case, a rook and a bishop on b2) that constitutes a Grimshaw. Second Example Valky River [1]
White to play and mate in two
The key in the puzzle on the right is 1. Qd2. This move has no threat, but it leaves black in zugzwang: Black must either move one of his bishops or rooks, or move a pawn. However, any bishop or rook move must unguard one of the squares of d5, d6, d7 or d8, allowing White to mate on d5, d6 or d7 with the queen, and d8 with the knight. The lines are:
Grimshaws involving pawnsThe pieces involved in Grimshaws are usually rook and bishop, as in the previous example, although Grimshaws involving pawns are also seen, as in this mate in two example by Frank Janet (published in the St.Louis Globe Democrat, 1916): Frank Janet, St.Louis Globe Democrat, 1916
White to play and mate in two
Multiple GrimshawsSometimes, multiple Grimshaws can be combined in one problem. Here are two examples by Lev Ilych Loshinsky each with three Grimshaws. First exampleLev Ilych Loshinsky, L'Italia Scacchistica, 1930
White to play and mate in two
This was first published in L'Italia Scacchistica, 1930. It is a mate in two. The key is 1.Rb1, with the threat 2.d4#. Each of Black's defences produces a Grimshaw interference which stops him from capturing White's mating piece. Black's defences, with White's replies, are:
There is one other black defence: 1...Rd6 leading to the simple recapture 2.Bxd6# (this is essentially the same mate as that which follows 1...Be6). Second exampleLev Ilych Loshinsky, Tijdschrift v.d. Nederlandse Schaakbond, 1930
White to play and mate in two
This second Loshinsky example, also a mate in two, is from Tijdschrift v.d. Nederlandse Schaakbond, 1930, and is one of the most famous of all chess problems. It is a complete block (if White could pass his first move, then he could reply to every black move with a mate), and White's key, 1.Bb3, holds this block, making no threat, but putting Black in zugzwang. Black has six defences leading to three Grimshaws, one of them a pawn Grimshaw:
After other black moves, White can play one of the above moves to mate; the three exceptions are 1...f5, taking away that square from the king and allowed 2.Qd6# and two recaptures: 1...Rxc7 2.Nxc7# and 1...Bxd4 2.Nxd4#. NovotnyA close relative of the Grimshaw is the Novotny, which is essentially a Grimshaw brought about by a white sacrifice on a square where it can be captured by two different black pieces – whichever black piece captures the white piece, it interferes with the other. ReferencesFurther reading
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