Walter Grimshaw (12 March 1832 – 27 December 1890) was a British author of chess problems. Such problems will generally declare white is to move first and within how many moves white must declare checkmate. The first move made is called the key to the problem, as there is always one, and only one, correct key to each problem. The number of moves is not a limit - it is a precise measure of how many moves a successful solution will take. Less is not more - less is less, as in less skillful, as a viable defense was likely overlooked. Walter Grimshaw was most famous for introducing a type of chess problem which won London's first chess puzzle tournament in 1854. The type of problem, bearing his surname to this day, relies upon the interference between two of the black's pieces to exploit an otherwise defended hole in black's defenses and achieve checkmate.

Before examining the position which won Grimshaw his namesake, let us first define interference on a chessboard. The limited range of the King and the Pawn, along with the non-linear movement of the Knight, limit interference with these pieces to coincidental affairs. In the world of chess problems, interference is generally a study of the movements of the Bishop, the Rook, and the Queen. Between these six pieces there are six different interactions. For similar linear movement we may consider two Rooks, a Rook and a Queen moving along the ranks and files, or a Bishop and a Queen moving along diagonals. For dissimilar linear movement we may consider a Bishop and a Rook, a Bishop and a Queen moving along the ranks and files, or a Rook and a Queen moving along diagonals. If there lies a square on the board which may be reached by both pieces in any pairing considered previously, that square would be a point of intersection between the two pieces. For illustration, the square marked with an "X" below would be the intersection between the Rook and the Bishop as placed.

We observe that, should the Rook move to the space marked ¤, the Bishop will be facing interference and will be unable to attack or defend the squares along the diagonal formed by e4, f3, g2, and h1. Should the Bishop move to ¤, the Rook will be facing interference and will be unable to attack or defend the squares along the file d7, d8. When both pieces in a pair may move to the same intersection, and the movement of either will interfere with the full range of motion of the other, they are said to be in mutual interference, which is the principle behind many of Grimshaw's chess problems. Ironically, the most challenging problem from his award winning set did not include a Grimshaw in its solution, but is nonetheless illustrated below to provide an example of the skill which led to this genre of chess problem, of which two examples are shared.

Walter Grimshaw
1st Prize set, Chess Player's Chronicle, 1852-1854

White to move. Mate in three.

 ♞ ♛ ♗ ♖ ♙ ♚ ♙ ♙ ♟

The problem shows black just on the cusp of gaining a material advantage, having pushed a pawn to the 7th rank. However, the situation is more bleak than it appears because white, while ignoring its own pawn advancement, has a stranglehold on six of the seven squares the enemy King could legally move to. The key to this problem is the sacrifice 1. Rf1. The primary defenses would play out as follows:

VariantWhiteBlackContinuationAnnotation
11. Rf1... exf12. Nf3 Kxf3 3. Rd2#Nf3 is threatening the pernicious Nd2 and must be addressed.
21. Rf1... f32. Rg1 (any) 3. Rg4#Here the black knight prevents the black queen from moving to any meaningful square.
31. Rf1... e82. Rxe8#Helpmate in 2 does not equal a Checkmate in 3.

A. G. Corrias
Problem 32, "Good Companion", 1917

Mate in two.

 ♔ ♕ ♚ ♟ ♟ ♜

This Grimshaw Interference problem, authored by A. G. Corrias, shows black with an abundance of material and two pawns pushed to the sixth rank. However, the object of the game is to checkmate the enemy king, and the sharks of white's remaining army are circling as black's king has no legal square to move to and is at the whim of white's next move. The key to this problem is the deflating 1. Qb1, which threatens immediate checkmate if the Queen is allowed to reach the b7-h1 diagonal. To this end, black may interpose to defend one of the squares, but not both.

VariantWhiteBlackContinuationAnnotation
11. Qb1... c32. Qd3#The pawn had temporarily given the black King an extra escape, but also caused interference with the Bishop.
21. Qb1... Bb22. Qh1#The Bishop prevents white from 2.Qb7#, but also interferes with the Rook and prevents the interposition 2...Rg2.
31. Qb1... Rb22. Qf5#The Rook prevents white from 2.Qb7#, but also interferes with the Bishop and prevents the interposition 2...Be5.

Frank Janet
St. Louis Globe Democrat, 1916

Mate in two.

 ♝ ♟ ♜ ♘ ♟ ♗ ♕ ♞

What's this? A chess problem of near equal material yet the black King is swarmed, with no legal square to move to? Surely, this sounds familiar by now. This is a problem similar to Corrias's, authored by Frank Janet. In the same vein as the previous problem, the solution lies not in a direct attack on the king, but the threat of a certain checkmate which draws black's pieces into interference. The key is 1. Qd7, where the threat of 2. Qf5# will prove to be unavoidable.

VariantWhiteBlackContinuationAnnotation
11. Qd7... Be62. Qxc7#The Bishop is able to protect against the response of 2. Qf5#, but also interferes with the Pawn and prevents the interposition 2...e5.
21. Qd7... e62. Qxa4#The Pawn is able to protect against the response of 2. Qf5#, but also interferes with the Bishop and prevents the interposition 2...Bc4.
31. Qd7... Ne62. Nd5#The Knight is able to interfere with Qf5#, but also interferes with the Bishop and prevents the capture 2... BxN.
31. Qd7... Ra5 2. Qd4#Defends Qf5#, but shows how Rook is overloaded. Does not illustrate a Grimshaw.
31. Qd7... Nxe32. fxe3#Defends Qf5#, but leads to immediate checkmate. Does not illustrate a Grimshaw.
31. Qd7... Ng32. fxg3#Defends Qf5#, but leads to immediate checkmate. Does not illustrate a Grimshaw.

ChessGames.com. "Walter Grimshaw"
Prize Winning Puzzle
Corrias "Grimshaw" Problem

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