Selfmates

The selfmate is a kind of orthodox problem that, like the helpmate, adheres to the standard rules of chess, but which involves an unconventional objective. In this type, 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.

In the first diagram, both kings are already immobilised (a common situation in selfmates) and the black pieces restricting the white king are themselves locked in. How does White manipulate Black’s only free piece, the queen, into giving mate? Suppose White starts by making a waiting move with the c1-bishop, such as 1.Bd2 (keeping guard on the g5-flight). Then Black must move the queen and a random placement, 1…Q~ (e.g. 1…Qa8/Qa4), will leave the piece controlling e4 and allow 2.Qe4+, forcing 2…Qxe4 mate. The black queen has various correction moves that foil 2.Qe4+ by preparing to intercept on f4 or g4, e.g. 1…Qe5 2.Qe4+? Qf4! But these queen moves inadvertently attack g3 or h3, enabling White to sacrifice the queen on these squares with check and compel new mates: 1…Qe5/Qf4/Qg6+/Qg4+/Qe3 2.Qg3+ Qxg3, and 1…Qe6/Qf5 2.Qh3+ Qxh3. The one exceptional defence is 1…Qe2!, which manages to target g4 without observing g3 or h3, and it thereby defeats the try 1.Bd2? The only way for White to handle this defence is to stop it altogether with 1.Be3!, the waiting key.

Problem 146 illustrates a typical way by which Black is compelled to mate in a selfmate – a black battery aimed at the white king is induced to open by a deflecting white check. Two such white checks seem to be arranged in the diagram, 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 preserve 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 1…Sa7/Sc7/Sc3/Sxa3, capturing the knight in each case – 2.Rxa7/dxc7/Sxc3/Rxa3, and 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 transference is 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.