Efim Rukhlis (1925-2007) was a Jewish chess player known for creating complicated and elegant chess problems for which the thematic variations were generally based upon interference of two or more pieces. The theme for which he is best known for creating, and still bears his namesake, involves puzzles with a change-mate, in which the solution achieves the same checkmate despite changes of defense among the variations. That statement is rife with jargon - before illustrating an example interference, let's make sure interference, change-mate, and variation are all clear.

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, rather than intentional ones. 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. If the pair in question share similar linear movement, as alluded to in the pipelink, we would identify these pieces as being in the situation of owning an intersection square and having the potential to be brought together by white under the device of Plachutta interference. If the pair in question share dissimilar linear movement, these pieces are in the situation of owning an intersection and have the potential to be brought together by white under Novotny interference.

Change-mate may be explained with equal plainness. A chess problem will have one key, the first move by white to which any response by black will be met by checkmate in the prescribed number of moves. The array of these responses are known as variations. A solution is labeled as involving a change-mate if there are situations where the same checkmate moves may be played by white in the face of different variations, or if multiple checkmates are viable for the same defensive position. In simple language, a Rukhlis theme is one in which white's checkmating combination is unaltered by two or more of black's potential responses to the key move.

Efim Rukhlis 1st Prize, Comite des sports de l`Ouzbekistan. 1955

White to play, mate in two.

     ♞ ♝ ♔ ♟ ♟ ♙ ♟ ♖ ♗

The position, orchestrated by Rukhlis, contains two examples of his namesake. It is also another type of change-mate as the checkmate solutions differ, but black's main line surrounds the defense of the threat brought to bear by the key 1. Qc7!. This move does nothing more than put immediate checkmate pressure on the f4 square (2.Qf4#), and also hold against any playable defense which black can muster. Thematically, as black attempts to reinforce f4 it finds itself victim to a variety of Grimshaw interferences, some standard and two of greater rarity.

• First Rukhlis at c1
• 1...g2 2.Qc1# Pushing the pawn to the second rank enables the black Queen to defend f4, but also creates a rare Pawn-Queen Grimshaw preventing the interposition 2...Qd2.
• 1...Qxh4 2.Qc1#
• Second Rukhlis at e5
• 1...Be5 2.Qxe5 The Bishop has protected f4, but black has walked headlong into a checkmate.
• 1...Bxg6 2.Qe5 The Bishop has protected f4, but in doing so has revealed that it was overloaded and in fact had to remain defending e5.
• Grimshaw examples with no Rukhlis device
• 1...N8e6 2.Ng4# The Knight from the 8th rank is able to competently defend f4, however it creates a rare Knight-Bishop Grimshaw on the cBishop without interposing with the Queens command of the dark square diagonal.
• 1...N4e6 2.Nf5# The Knight from the 4th rank is able to competently defend f4, however it creates a rare Knight-Bishop Grimshaw on the cBishop without interposing with the Queens command of the dark square diagonal.
• 1...Ne2 2.Nc3# The Knight has a second method to defend f4, but this is no better than the previous variation as it creates a rare Knight-Queen Grimshaw such that 2.Qxc3 is eliminated as a saving move.

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