Selfmates

The selfmate is a genre of orthodox problems that, like the helpmate, adheres to the standard rules of chess, but which involves an unconventional objective. Here the solver has to discover how White, moving first, can force Black to deliver mate. Black does not cooperate and tries to avoid giving mate for as long as possible. As in directmates, White has only one key capable of achieving the task in the specified number of moves, and the play consists of various black defences and White’s correct responses to them, but in selfmates each variation finishes with a forced mating move by Black.

A black mating move can be induced in one of two general ways: White’s final move either puts Black in zugzwang or gives a deflecting check. Both possibilities are illustrated in our first example. The two kings are already immobilised (a common situation in selfmates), and since the knight is pinned, Black has only two legal pawn moves, one of which would give mate on a2. Set play is arranged for 1…cxb4, when 2.Qxb4 re-pins the knight and compels 2…a2 by zugzwang. However, White has no waiting move capable of preserving the set line, e.g. 1.Bg3? cxb4! 2.Qxb4 Ke3; 1.Qe7? cxb4 2.Qxb4, but 1…Kc3! refutes. The key 1.Bd6! (waiting) unguards e3 but controls c5, then 1…cxb4 is followed by a changed response, 2.Qd2+, a deflecting check that exploits the unpinned knight, forcing 2…Sxd2 mate.

Problem 146 employs a typical device by which Black is forced to mate in a selfmate – a black battery aimed at the white king is induced to open by a deflection. Two such white checks seem prepared to trigger Black’s R + B battery, but it would be premature to play them: 1.Rb3+? Bxb3+ is not mate because of 2.Bf1, and 1.Se2+? Bxe2+ similarly prompts 2.Rd1. The key 1.Qe6! threatens 2.Qb3+ Bxb3. Black cannot defend by moving the g1-rook off the rank, since the threat will still work with a battery mate given by the other black rook. So Black has only two defences, knight moves that prevent the queen from reaching b3. 1…Sc4, however, also prospectively closes the white bishop’s line and hence admits 2.Rb3+ Bxb3. Likewise, 1…Sd5 cuts off the white rook on the d-file, facilitating 2.Se2+ Bxe2.

In Problem 147, Black’s mating moves are forced by zugzwang. If White could eliminate the b5-knight without checking or releasing the black king, Black must play the only legal move left, …g2 mate. Hence we have set play that deals with each knight move: 1…Sa7 2.Rxa7, 1…Sc7 2.dxc7, 1…Sxd6 2.Sxd6, 1…Sxd4 2.Sxd4, 1…Sc3 2.Sxc3, 1…Sxa3 2.Rxa3. White is unable to maintain all of these variations, though, and the key is the surprising 1.Sxg3! (waiting). This move removes the mating pawn but frees the h1-knight to mate on g3 instead. White proceeds as set against four defences, 1…Sa7 2.Rxa7, 1…Sc7 2.dxc7, 1…Sc3 2.Sxc3, and 1…Sxa3 2.Rxa3, forcing 2…Sxg3. But the responses to 1…Sxd6 and 1…Sxd4 are now replaced by 2.Qe7 and 2.Qe4 respectively, pinning the knight. The changed play is made possible by the new mating move 2…Sxg3, which covers the e2-flight so that the queen no longer needs to block it.

Four excellent thematic tries with subtle refutations are featured in the next problem. The white rook executes these tries and the key by moving along the b-file, so as to unguard d3 for the threat, 2.Qd3+ Bxd3. Black defends by interfering with the bishop’s access to d3, and 1...d3 also disables the threat (2.Qxd3+? Rxd3!). These defences, however, not only unpin the white queen but also set up a masked black battery formed by the defending piece and bishop, allowing the queen to give a deflecting check that forces the battery to open. This scheme requires White to start carefully with 1.Rb8!, because if placed elsewhere on the b-file, the rook will interrupt one of the battery mates. 1…f5 2.Qg4+ fxg4, 1…Rg6 2.Qg4+ Rxg4, 1…Rf5 2.Qf3+ Rxf3, and 1…d3 2.Qe2+ dxe2. There’s by-play with 1…Sc2/Sb3 2.Qc2+ Bxc2. The tries are 1.Rb7? f5! 2.Qg4+ fxg4+ 3.Rxh7, 1.Rb6? Rg6! 2.Qg4+ Rxg4+ 3.Rg6, 1.Rb5? Rf5! 2.Qf3+ Rxf3+ 3.Rf5, and 1.Rb4? d3! 2.Qe2+ dxe2+ 3.Re4.

The marvellous 149 delivers complex but lucid changed play. The set play involves three captures of the white bishop, two of which produce diagonal battery mates: 1…Rxc6 2.Qc4+ Rxc4, 1…Sxc6 2.Qd4+ Sxd4, and 1…Qxc6+ 2.Qe4+ Qxe4. The key 1.Qxf4!, by self-pinning the queen, threatens 2.Be4+ Qxe4. The two battery-creating captures on c6 are answered by new continuations, again made possible by the pin of the queen: 1…Rxc6 2.Sc5+ Rxc5 and 1…Sxc6 2.Sb4+ Sxb4 (while 1…Qxc6 mates immediately). Black can also parry the threat by unpinning the queen, and these defences bring back the white second moves seen in the set variations – 1…Bf7 2.Qc4+ Bxc4, 1…Bf6 2.Qd4+ Bxd4, and 1…Sf6 2.Qe4+ Sxe4 – now generating three orthogonal battery mates. The white queen checks are thus transferred to new defences relative to the set play. When such move transferences are combined with changed white replies to the same defences (1…Rxc6/Sxc6), the Rukhlis theme is accomplished – a pattern more familiar in directmate problems. Lastly, there’s a subsidiary variation that also shows good battery play: 1…Rb7 2.Bb5+ Rxb5.