Novotny Interference (sometimes referred to as "Nowotny") is a special type of Grimshaw found in chess problems, wherein the black side has either been lured or forced into accepting a sacrifice by the white side, thus entering two or more of its own similar moving pieces into mutual interference. 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 trick to chess problems of this type is that the key will generally be a sacrifice to create the Novotny Interference. The device is named after its discoverer Antonín Novotný.

Before examining a position illustrating this artificial Grimshaw, let us first inspect the situation by which a sacrifice could create 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. A Novotny device is concerned only with the interactions of dissimilar linear movements. If there lies such a square on the board which may be reached by both pieces in any dissimilar linear movement pairing considered previously, that square would be a point of intersection between the two pieces. Should any enemy piece reach such an intersection, whose presence would otherwise lead to a checkmate, we may consider the sacrifice by white to be forced upon black. Let us pretend that the black King below cannot move to any square marked Z, and no other piece is capable of interposition. Should the white Queen move to the intersection square ¤, black would be compelled to capture the queen, thus interferring with the piece which had not moved.

     ♚ Z Z Z ♕ ♜

Such a position would be rare to see in a chess problem, let alone in a real game. The basic example below will illustrate how the sacrifice is often forced to prevent one checkmate, only to admit defeat to another.

Unattributed
Wikipedia. "Novotny (chess)". Accessed January 2012.

White to play and mate in two.

 ♟ ♘ ♙ ♜ ♙

The root of the problem above lies in the identification of the adjacent Bishop and Rook in combination with the precarious position of the black King. The key is 1. Nb2, as it opens up an unavoidable mainline leading to checkmate from the white Queen.

• 1...Rb2 2.Qd4# The Rook prevents the response 2.Qf2+, but also interferes with the Bishop and prevents the capture 2...Bxd4. 2...exd4 is not a legal move as the Pawn is pinned by the Bishop at d6.
• 1...Bb2 2.Qf2# The Bishop prevents the response 2.Qd4+, but also interferes with the Rook and prevents the capture 2...Rxf2.

R.C.O. Matthews
"British Chess Magazine", 1957

White to move and mate in three.

♜ ♝ ♖ ♖ ♜ ♙ ♟ ♙ ♙ ♕ ♗ ♘ ♙ ♟ ♞ ♞

A glut of material is present on the board, which means nobody is surprised that the black King has not a single square to move to. This three move problem has a single key, after which each of black's six responses lead directly to a Novotny device from white, leading ultimately to checkmate. The key is 1. b4, which threatens the mainline 2.Bxb1 3.Ra3#.

• 1...Bb6 2.Rd5. Creates a Novotny device against the a8Bishop and h5Rook. 2...Bxd5 is met by 3. Nb5#, while 2...Rxd5 is met by 3.Ne4#. Any other second move leads to a checkmate from the same Knight.
• 1...Rbxb5 2.Qd5 Creates a Novotny device against the a8Bishop and both Rooks. The same interferences and results will play out as we saw from the 1...Bb6 response.
• 1...Bc5 2.Rb7 Creates a Novotny device against the a8Bishop and b8Rook. The same interferences and results will play out as we saw from the 1...Bb6 response.
• 1...Bb7 2.Rc5 Creates a Novotny device against the a7Bishop and the h5Rook. 2...Bxc5 is met by 3.Nb5#, while 2...Rxc5 is met by 3.Bxd4#. Any other second move leads to a checkmate from either piece.
• 1...Bd5 2.Rbb6 Creates a Novotny device against the a7Bishop and the h5Rook. The same interferences and results will play out as we saw from the 1...Bb7 response.
• 1...Rhxb5 2.Rb6 Creates a Novotny device against the a7Bishop and both Rooks. The same interferences and results will play out as we saw from the 1...Bb7 response.

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