In directmate problems, the idea of changed play can be separated into two categories.

The more familiar one, changed mates, means that in two phases of play the same black defence leads to different white mating responses.

The less usual type, known as mate transference, reverses the situation: in two phases, the same white mating move is induced by different black defences.  In other words, a white mate that’s effective against one black defence is surprisingly ‘transferred’ to another black move.

Problem 110 illustrates mate transference along with focal play.

The black rook in the diagram is ‘focusing’ on d5 and g4, the white knight’s mating squares.  If Black moves the rook, the focus is lost and one of these squares will be left unprotected, yielding the set lines 1…R- on rank 2.Nd5, and 1…R- on file 2.Nxg4.

However, the first move 1.Qa1! (waiting) pins the rook, and simultaneously unpins the black bishop.  The latter now takes over as the thematic defender, and when it moves, the piece similarly loses the focus and enables the knight mates to recur: 1…Be2/d1 2.Nd5, and 1…B- others 2.Nxg4.

There is by-play 1…c4 2.Qxd4 and 1…d5 2.Qa6.

110. Michael Lipton
U. S. Problem Bulletin 1963
2nd Prize

Mate in 2

Problem 111 presents such a scheme, a combination of mate transference and changed mates.  The set variations are 1…cxd3 2.Nb3 and 1…exd3 2.Nf3, in which White takes advantage of the simple un-guards by Black’s pawns.

The key 1.Qxd7! (waiting) grants two flights to Black, and the ensuing king moves provoke the knight mates we have just seen, 1…Kc5 2.Nb3 and 1…Ke5 2.Nf3.

111. Efren Petite
Die Schwalbe 1996

Mate in 2

But in addition, the set defences by the pawns are followed by a new pair of mates, 1…cxd3 2.Rxe4 and 1…exd3 2.Rxc4.  Now these pawn moves commit a different type of error, the opening of a white rook’s line to cover a flight.
 

The key 1.d4! cuts off the a4-rook and a7-bishop, but neither knight mate is threatened because of the pin formed on the second rank.  White threatens 2.Qf3 instead, since the key-pawn has placed an extra guard on e5.  When Black defends with the h2-rook, the knight is released and so allowed to mate again: 1…Rh4 2.Ne3 and 1…Rh3 2.Nf4, i.e. the knight mates are transferred to these unpinning defences.

Meanwhile, Black’s moves to d4 have changed their effects, from self-interferences to self-pins, and these errors are exploited accordingly with 1…Rxd4 2.Bc4 and 1…Bxd4 2.Rc5 – two pin-mates.  (1…Rxg2+ 2.Bxg2, 1…Nxg5 2.Qe5, 1…Qe6 2.Qxe6, and 1…Qxe7 2.Qc6.)

112. John Rice
The Problemist 1967
2nd Hon. Mention

Mate in 2

The blending of mate transference and changed mates is further enhanced in the so-called Ideal Rukhlis.

In Problem 113, the double-checks Nd4 and Ne5 do not mate immediately because they interfere with lines controlled by the g1-bishop and g5-rook, respectively.  Black allows these double-checks to work in the set play, after self-blocking on b6 and b5: 1…Bb6 2.Nd4, and 1…Nb5 2.Ne5.

Two more important set lines are 1…Qh2 2.Nxh2 and 1…Qd2+ Nxd2, making further use of the Q + N battery.

White starts with 1.Qb2! (threat: 2.Qb7), which observes b6 and b5 but relinquishes the battery set-up.  Now the knight mates are prevented for a different reason – direct guards by Black’s queen, hence the transferred mates when the queen tries to stop the threat by pinning White’s queen, 1…Qh2 2.Nd4, and 1…Qd2 2.Ne5.

113. Marjan Kovacevic
The Problemist 1993
3rd Prize

Mate in 2

Have a go at solving Problem 114, which makes its point vividly.  The solution will appear next month.

114. Srinivas Mantha
The Problemist 1992

Mate in 2

108. Martin Hoffmann
Die Schwalbe 1990
6th Hon. Mention

SPG in 8

1.e3 d6 2.Ba6 Bh3 3.Qg4 Qd7 4.Nf3 Qb5 5.Rf1 Qxf1+ 6.Bxf1 Na6 7.d3 Rc8 8.Qxc8+ Bxc8.

Both 2.Ba6 and 2…Bh3 are clearance moves, designed to allow another piece (the opposing queen in each case) to travel along the line just traversed by the clearing piece.