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251. Christer Jonsson
Australasian Chess 2012
Helpmate in 2
2 solutions

Helpmates in which the black king moves to another square to be mated are often tricky to solve. Such is the case here, as the black king walks into a double-pin model mate in each solution: 1.f4 Sb3+ 2.Ke3 Rh3 and 1.Re6 Re2 2.Ke5 Sc6. That the pins are all constructed in the course of play, rather than pre-existing in the diagram, is considered an important feature. White’s knight, bishop, and h2-rook all change their roles in the two parts, acting variously as a guard, pinner or mating piece, though we don’t see an interchange of functions between any two pieces.

252. Frederick Gamage
Chess World 1946
1st Prize
Mate in 2

The key 1.d7! threatens 2.d8(Q) and allows Black to check on the rank. White activates the Q + B battery on the g-file when the black rook interferes with b7-bishop: 1…Rd5 2.Be5 and 1…Rc6+ 2.Bf6. The b7-bishop cuts off the black rook in turn with 1…Bc6 2.Rc8, producing a Grimshaw. Another interference occurs in 1…Re5 2.Sf6, while the same mate results from 1…Bf6 2.Sxf6. Lastly 1…Bxg7+ forces 2.Qxg7, a variation that makes good economical use of the white queen.

Jacob Hoover: I found the many self-interferences appealing (especially the Grimshaw pair) but the repeated mate (2.Sf6) I didn't like very much.
Nigel Nettheim: Very neat play, including Grimshaw interferences on c6 and single interferences on d5 and e5.

253. F. W. Walton
Time & Tide 1954
Mate in 2

White mates are prepared against all possible black moves in the initial position. 1…Se~ opens the first rank and permits 2.Qb1, while the correction 1…Sc2 is a self-block that leads to a white self-interference mate, 2.Sb2. Any black bishop move enables the white rook to control e2: 1…B~ 2.Qxe2. Yet another line-opening error is committed by Black in 1…e3 2.Qf5. And 1…Sb~ is an unguard that allows 2.Sc5. White has many tries that aim to preserve the set play, but they are refuted thus: 1.Ke8? Sd6+!, 1.Ke7? Bg5+!, 1.B~? Bh6+!, and 1.Rb2? Sc2! Only 1.Kg8! works, a waiting move that retains all of the set variations.

Jacob Hoover: The key utilises the only square the king can move to where he can't be immediately checked.
Nigel Nettheim: It is amusing that the white king simply dodges checking defences; it is set on its optimal square, immobilizing the white bishop.

254. Leonid Makaronez &
Leonid Ljubashevskij

Australian Chess 2005
Mate in 3

White could aim for a rook mate on h8 by opening the top rank, but such moves by the king are defeated if played immediately: 1.Kc7? Rxc4+!, 1.Kxd7? Qxd4+!, and 1.Ke7? Rxe5+! The superb key 1.Qd1! shows a triple sacrifice, and it threatens 2.g5+ fxg5 3.Bxg5. Black’s major pieces are decoyed in the variations, 1…Rcxd1 2.Kc7 and 3.Rh8, 1…Rexd1 2.Ke7 and 3.Rh8, and 1…Qe2 2.Kxd7 and 3.Rh8. If 1…Qxd1, the black queen loses control of the half-battery on the h-file, admitting 2.Bg5+ fxg5 3.Sg1. The half-battery operates again in 1…Re2 2.Bg5+ fxg5 3.Sf2. There’s by-play with 1…f3 2.Qxd2+ Re3 3.Qxe3, when the white queen dispatches two of its own capturers from the main variations!

Nigel Nettheim: An amazing key, controlling h5 for the threat and, more importantly, overloading the black pieces.
Jacob Hoover: A highly unified problem.

255. Geoff Foster
Chess in Australia 1986
Mate in 2

An excellent key, 1.Sc4!, sacrifices the knight and yields two flights to the black king. The threat of 2.Qc6 is answered by the h4-bishop in two thematic variations, 1…Bf6 2.Sg5 and 1…Be7+ 2.Sd6. In each case the bishop interferes with a pinned rook that could potentially defuse the B + S battery, allowing White to unpin the piece with impunity when opening the battery with the knight, which needs to re-guard the e4-flight. The battery fires again if Black accepts the sacrifice – 1…Kxc4 2.Se5, while taking the other flight leads to 1…Ke4 2.Qxf5. Lastly, 1…Rd6 2.Sxd6 shows a mate similar to that in one of the main variations. The late Brian Tomson remarked when this problem was first published, “A sophisticated two-mover.”

Nigel Nettheim: The key must be made with the d6-knight, but its destination is determined with intricacy. A highlight is the cross-check after 1…Be7+.
Jacob Hoover: Another problem that involves my favourite chess problem theme – battery play.

256. John James O’Keefe &
Joseph Heydon

The Brisbane Courier 1921
Mate in 2

A nice withdrawal key 1.Be8! threatens 2.Bg6. The white queen, initially pinned by its counterpart on the long diagonal, is freed remarkably five times to give various mates. Three such unpins occur by interposition: 1…Sc3 2.Qe3, 1…c3 2.Qxd5, and 1…d4 2.Qg3. The rest are direct unpins by the black queen: 1…Qb6 2.Qf5 and 1…Qxe2 2.Qxe2. The two queens share one more variation in 1…Qd4 2.Qxd4. Lastly, the g4-knight delivers two mates in the by-play, 1…Qxe5+ 2.Sxe5 and 1…Sg5/Sf4/Sf2 2.Sf2.

Jacob Hoover: Several black defences unpin the queen.
Dennis Hale: At first glance, 1…Qb6 seems to defeat 1.Be8; it defends both g6 and e3 and hence prevents 2.Qe3, but White has 2.Qf5. It is a nice symmetry that the key and its threat involve a long forward move (1.Be8) and a long backward move (2.Bg6), and the most promising defence and its aim involve a long forward move (1…Qb6) and a long backward move (2…Qe3).
Nigel Nettheim: Good, if not truly memorable. The h2-pawn prepares 1.Bxb2? hxg1(Q)!; the g2-pawn then disarms 1…h1(Q) after 1.Be8!

257. Christopher Jones
Australian Chess 2005
Helpmate in 3
Twin (b) BQg6

The black king has four accessible squares initially, and intricate play is required to organise a mate that covers all of these flights. In part (a), White plans for a bishop mate on f5, which necessitates support from the white king and a clearance capture by a black piece: 1.Sf4 Ke7 2.Se3 Kxf6 3.Sxf5 Bxf5. After a self-block on f4, Black uses the c4-knight (rather than the h5-bishop) for capturing on f5, so as to allow the white rook to guard d4. Part (b) has a black queen starting on g6, and the resulting solution shows an orthogonal-diagonal transformation of the strategy seen previously: 1.Se5+ Kxd6 2.Qg1 Kc5 3.Qxd4+ Rxd4. The rook mate on d4 motivates the white king’s different approaching moves. Black’s self-block on e5 is followed by the queen’s clearance capture on d4, which also helps the white bishop to control f5. The two white line-pieces therefore exchange their roles in the two parts, and so do the black pieces on c4 and g6, although curiously the identity of the g6-piece is different in each case.

258. William James Smith
Australasian Chess Magazine 1920
Mate in 2

In this complete block position, white mates are arranged for all possible black moves: 1…Kxc5 2.Qd6, 1…Sb~ 2.Rc4, 1…Sg~ 2.Qf2, and 1…Se3 2.Qe5. But White has no simple waiting move that could maintain all of these set variations. After 1.Qd2! (waiting), the queen loses control of e5 and d6 but attacks c3 and is also ready to support the d-pawn. Now three of the four variations involve changed mates: 1…Kxc5 2.d4, 1…Sb~ 2.Rd5, 1…Sg~ 2.Qf2, and 1…Se3 2.Qc3. This mutate has two good tries that show more changed play: 1.Sd1? 1…Sg~ 2.Qe3, but 1…Kxd3! refutes, and 1.Qc1? 1…Sg~ 2.Qg1, but 1…Sf2! refutes.

Andy Sag: Note the thirteen pieces. Can it be reduced to twelve? Tried removing the g3-pawn but then 1.Qg3 is a cook. However, you can actually remove that pawn if the queen starts from d2; then the key 1.Qf4! is sound and you still get three changed mates.

259. Comins Mansfield
The Brisbane Courier 1924
4th Hon. Mention
Mate in 2

The key 1.Sc4! shuts off the black queen to threaten 2.e4. A wealth of strategically interesting play follows, with the black knights having a starring role in five of the eight variations. First the pair allow the R + B battery to operate by interfering with the f7-pawn: 1…Sgf6 2.Bxd7 and 1…Sdf6 2.Bxg4. Next they unguard a mating square and cut off the g1-bishop: 1…Sf2 2.Se3 and 1…Sc5 2.Sxb6. Lastly the g4-knight closes the same bishop line with 1…Se3 2.Qxd3. Another interference on e3 occurs in 1…Be3 2.Qh1, when the unpinned rook cannot interpose on the long diagonal. The self-block 1…Re6 enables White to utilise the battery once more: 2.Be4. Only one variation, 1…Qxc4 2.bxc4, lacks any line effects.

Dennis Hale: My favourite variation is 1…Be3 2.Qh1. Nice to see a problem from the great English composer.

260. Andy Sag
OzProblems.com 2015
Mate in 2

There is significant set play consisting of 1…Rxd5 2.Qxd5, 1…Sxf5 2.Rxf5, and 1…a2 Qb2. The white queen takes a backward step with 1.Qe1! to subtly threaten a corner mate (2.Qa1), and also grants a flight on d4. The three set variations are abandoned by the key, but two of these set defences result in unexpected new mates given by the Q + P battery: 1…Rxd5 2.exd5 and 1…Sxf5 2.exf5. A third battery mate delivered by the e-pawn follows if Black takes the flight: 1…Kd4 2.e5. Additional variations are 1…b3 2.Qc3, 1…Rxc4 2.Bf6, and 1…Se6 2.Sxc6.

Composer: Two tries are 1.Qd1? (2.Qa1) b3! and 1.dxc6? (2.Qd6 and 2.Rxa5) Sb7! The latter is aggressive but the point of interest is that by occupying c6 the white pawn prevents 2.Sxc6, leaving the d8-knight free to move to b7 which neatly defends both threats. The d8-knight also prevents 1.Rxc6 from being a cook by defusing 2.Re6, thus leaving the h6-knight free to move to stop 2.Bf6.
Paz Einat: Excellent key with two mate changes and central role for the pawn battery.
Jacob Hoover: Nice one, Andy. It's always a pleasure (at least for me!) to see the battery play in action.

It’s a pity that this fine two-mover is largely anticipated by the problem below, as reported by Geoff Foster. He writes, “This is very similar to Andy's, with the extra nice feature of the thematic black defences being checks, making the set play more noticeable.”

Meindert Niemeijer
The Problemist 1973
4th Prize
Mate in 2

Set play: 1…Bxe5+ 2.Qxe5 and 1…Rc5+ 2.Rxc5. Key: 1.Qd1! (2.Qh1). 1…Bxe5+ 2.dxe5, 1…Rc5+ 2.dxc5, 1…Ke4 2.d5, and 1…g3 2.Qf3.

261. Stanislovas Vertelka
Australian Chess Problem Magazine 1994
Helpmate in 2
3 solutions

The solutions are 1.Sfxd5+ Qg7 2.Sf6 Qg1, 1.Sbxd5+ Qc5 2.Sb6 Qf5, and 1.Bxd5+ Qb4 2.Bc4 Qe1. White does not have time to move the d-pawn to let the a8-bishop control the flights on f3 and g2, because the white queen will require two moves to set up a mate. So Black aims to open the long diagonal for White by removing the d-pawn. Each possible capture of the d-pawn is also a discovered check, however, and this determines the white queen’s first move which must answer the check by interposition. The queen move is thus a self-pin. And when the black piece on d5 moves to open the long diagonal, it performs a switchback so as to unpin the queen, which is freed to give a different mate each time. Three closely matched solutions showing good strategic effects.

262. Andy Sag
OzProblems.com 2015
Mate in 2

The a6-bishop’s half-pin of two black pieces produces the set variation, 1…R~ 2.Se3. A good withdrawal key 1.Bc8! gives up the half-pin and threatens 2.Bxh3. Now 1…Rf5/Rh5 is answered by the changed mate 2.Qa1. A second corner-to-corner queen mate occurs with 1…Sf5 2.Qh1. After 1…B~, the queen delivers yet another long-range mate, 2.Qg2. There’s one line of by-play: 1…Se3 2.Sxe3.

Composer: Meredith (twelve-piece) setting with threat and four variations, one changed mate, and two tries, 1.Qf3? (2.Qd1) Re5! and 1.Bxb5? (2.Qa1/Se3) Se2! The latter defence unpins the c4-knight so neatly defends against both threats; also this move of the g3-knight still maintains a defence against 2.Qh1 as it can then interpose on g1.
Jacob Hoover: The queen is pretty much the star of the show, delivering almost every mate in the actual play. As far as I'm concerned this counts as a theme, which I have taken to calling “Girl Power.” Another great one, Andy. The half-pin red herring made it memorable.

263. Adrian Berkel
The Brisbane Courier 1917
Mate in 2

Set mates are prepared for all possible black moves in the diagram. The waiting key 1.Kd2! largely preserves the set play while adding two more variations. Two black defences open lines for the white queen: 1…R~ 2.Qe5 and 1…Bg8 2.Qh1. The e7-pawn commits three self-blocks: 1…e5 2.Sgf6, 1…e6 2.Bc6, and 1…exd6 2.Sef6 (the set dual 2.Sef6/Sc7 has been removed). The added play consists of the flight-taking 1…Ke4 2.Bc6 and a nice en passant avoidance, 1…d3 2.e4.

Jacob Hoover: A random king move grants a flight on e4 that is answered with 2.Bc6, but 1.Kc2? fails to 1…d3+! Only 1.Kd2! works, answering 1…d3 with the pin-mate 2.e4.

264. H. Beechey
The Brisbane Courier 1926
2nd Hon. Mention
Mate in 2

The key 1.Sf7! covers d6 so as to threaten 2.Sd7, which interferes with the white queen’s control of the d-file. The d4-knight and e3-queen are half-pinned by the white bishop, and when either moves off the diagonal to answer the threat, White could exploit the pin of the remaining black piece. Any move by the knight on d4 defends by vacating that square for the king, and leads to two potential mates by the g2-rook; but in every case the knight move has an arrival effect that forces a single mate: 1…Se2/Sb5 2.Rg5 and 1…Sxb3/Sc6/Sxe6/Sf5/Sf3 2.Rxc2. The black queen has two capture defences aimed at creating more flights: 1…Qxe4 2.Qa5 and 1…Qxb3 2.Qc7. Four different pin-mates are hence realised in these thematic variations.

Jacob Hoover: 1…Qxe4 2.Qa5 shows a change from the set play, 1…Qxe4 2.Sxe4. A quite lovely demonstration of the half-pin theme, with no by-play at all.

265. Frederick Hawes
problem 1962
Mate in 3

This miniature is solved by a withdrawal key 1.Ba6!, which grants a flight on g2 and entails two threats: 2.Bb7+ Bg2 3.Rd1 and 2.Rd1+ Bf1/Kg2 3.Bb7. These threats are separated or individually forced by 1…Bf1 2.Bb7+ Bg2 3.Rd1 and 1…Bg2 2.Rd1+ Bf1 3.Bb7. The remaining defences are all answered by the same bishop check, though a variety of mates follows. 1…Kg2 2.Bb7+ Kf1 3.Rd1, 1…Bxd7 2.Bb7+ Bc6 3.Bxc6, 1…Be6 2.Bb7+ Bd5 3.Bxd5, 1…Bf5 2.Bb7+ Be4 3.Bxe4, and 1…Bg4 2.Bb7+ Bf3 3.Bxf3. Not 1.Be2? (2.Bf3+/Rd1+) Bg4! or 1.Bb5? (2.Bc6+/Rd1+) Bxd7!

Jacob Hoover: This problem was way too easy… or I've gotten a lot better at three-movers by now. Either way, this miniature was a nice one.
Nigel Nettheim: Easy to solve, but nice. It seems surprising that this could be done with no short mates or duals (apart from the dual threats).

266. Robert Lincoln
Australian Chess Problem Magazine 1995
Mate in 2

The thematic try 1.Sg6? threatens 2.Se7 but also cuts off the h7-bishop’s control of e4. 1…Bh4 is answered by 2.Sgf4 (re-opening the bishop-line) and not 2.Sdf4? which would create a flight on e4 by closing the g4-rook’s line. 1…Ra7 permits another knight mate, 2.Sb4. But 1…Qh4! defeats the try because 2.Be4 is disabled. The key 1.Sc6!, with the same threat as the try, interferes with the c8-rook’s control of c5. Now 1…Bh4 provokes a new mate, 2.Sf4. After 1…Ra7, White must choose 2.Scb4 – another changed mate – and not 2.Sdb4? which would allow the king to escape to c5 by closing the a3-bishop’s line. The changes between the try and post-key phases are brought about with sophisticated and closely matching line strategy. The by-play consists of 1…Qh4 2.Be4 and 1…e5 2.Bg8.

267. Molham Hassan &
Andy Sag

OzProblems.com 2016
Mate in 2

The key 1.Qf8! prepares for an indirect battery mate, 2.Sb5, in which the opened queen-line to c5 compensates for the closure of the a5-rook’s line to the same square. Two pawn-takes-pawn defences are exploited by White as square-clearances: 1…exf2 2.Bxf2 and 1…dxc6 2.Sxc6. A couple of black moves open lines for white pieces which traverse them to give mate on the long diagonal: 1…Sxd6 2.Qf6 and 1…Rb2 2.Bxc3. The a2-bishop defends twice and is captured by the c5-rook each time: 1…Bc4 2.Rxc4 and 1…Bd5 2.Rxd5. Three corresponding pairs of variations are thereby presented. Moreover, co-composer Andy Sag claims a fourth pair of related mates in that 1…Sxf5+ 2.Sxf5 and the threat of 2.Sb5 share the same mating piece. A debatable point, but either way this is a splendid problem that shows an uncommon theme.

Andy Sag: To complete the Christmas “pair” tree, we have two tries defeated by the black bishop pair: 1.Qe8? (2.Qe4/Qxe3/fxe3) Be6! and 1.Bxd2? (2.Bxc3/Bxe3/fxe3) Bxd2!
Jacob Hoover: This was a pretty nice problem, but I feel the solution was a little too obvious in that the queen is the only white unit not doing anything in the diagrammed position.

268. H. Cox
Chess World 1948
Mate in 2

Set mates are arranged for all possible black moves in the initial position, but White has no simple waiting move available, e.g. 1.Kh4? Sf3+! The key 1.Bg5! (waiting) unguards e5 so that after 1…e5 the set mate 2.fxe5 no longer works, but now with the queen shielded from the black rook, White can afford to unpin the latter with 2.f5 – a changed battery mate. The key also frees the f7-pawn to add the variations 1…f6 2.Qxe6 and 1…f5 2.Qe2, both of which require the key-bishop to take over the control of f4. The rest of the play is as set and also dual-free: 1…Sxb3/Sf3 2.Re2, 1…Sf1/Sc4 2.Rc4, 1…Sb~ 2.Sxd2, and 1…d5 2.Sc5. More tries that aim to maintain the block include 1.Ra2? Sf1 2.Ra4, but 1…Sc4!; 1.Rc5? Sd~ 2.Qf3/Rc4, but 1…d5!; 1.Qg5? e5! and 1.Be5? f6!

269. Chris Feather
Australasian Chess 2011
Helpmate in 5
Twin (b) Pb2 to c5

In part (a), a bishop mate cannot be organised because there are not enough black pieces in the king’s vicinity to block all of its flights. Instead, White aims for a queen-promotion mate on c8, which requires Black to sacrifice a piece on c7. The job goes to the b2-pawn, and it must promote to a queen in order to reach c7 in time. Remarkably though, Black begins with 1.e5, the sole waiting move that won’t disrupt the plan. 1…Bc2 2.b1(Q)+ Bd1 3.Qh7 Bb3 4.Qc7 bxc7 5.b6 c8(Q). Part (b) has the b2-pawn shifted to c5, where it blocks a flight. Now a bishop mate along the long diagonal is possible, but a white queen promotion is still necessary to cover all of the flights. This time White clears a path for the pawn by removing the one on b7. Meanwhile, the black king needs to get out of the way of not only the white bishop but also the black one, to allow the latter to self-block on d7. 1.Kd5 Be4+ 2.Kc4 Bxb7 3.Bd7 Ba8 4.Kb5 b7 5.Kc6 b8(Q). A battery mate completes an appealing sequence in which the black king performs a rundlauf, or round-trip back to its original square.

Andy Sag: What makes part (b) so diabolically difficult is that the king goes round a circle and ends up where it started. The e6-pawn does not participate directly but provides the only first move in part (a) that does not mess up the setting, and in part (b) prevents a cook in which the black bishop gets to d7 via e6.

270. William J. McArthur
The Leader 1918
Australian Columns Tourney
2nd-3rd Prize
Mate in 3

The key 1.Rh3! removes a flight on f3 but grants another one on f5. The threat is 2.Qg5+ Kxh3 3.Qg3, against which Black has six defences that lead to three pairs of interrelated variations. 1…f1(S) frees the b5-knight since Black no longer has …f1(Q)+ available; now 2.Sbd6 threatens 3.Qh4; 2…Bf6 3.Sxf6 and 2…Sg3 3.Rxg3. Another pawn defence, 1…f6, by obstructing …Bf6, allows similar play by the other white knight: 2.Sed6 and there’s no stopping 3.Qh4. Black commits the error of a distant self-block in 1…Sxe4 2.Qh5+ Kf4 3.Rf3 and again in 1…Be5 2.Qh5+ Kf4 3.Qf3, with a different mate on f3 in each case. And two unguarding moves enable White to check with the e4-knight, followed by a rook switchback mate: 1…Se2 2.Sxf2+ Kf5 3.Rh5 and 1…Bf6 2.Sxf6+ Kf5 3.Rh5. If Black takes the flight with 1…Kf5, then 2.Qg5+ Kxe4 3.Re3. This great problem shows complete accuracy of play in its seven full-length variations.

Jacob Hoover: The additional variation 1…Kf5 2.Qg5+ Kxe4 3.Re3 gives an echo mate with respect to 1…Sxe4 2.Qh5+ Kf4 3.Rf3. So four pairs of similarly-themed variations exist! This was a nice one, which kept me stumped for two days.
Andy Sag: “Give-and-take” key. The a2-rook and b1-bishop appear to be redundant and could be removed, reducing the setting to thirteen pieces.

271. Eric M. Hassberg
Check! 1945
Mate in 2

Most of Black’s available moves are provided with set mates, with the exceptions of 1…Qc3 and 1…Qc2. The waiting try 1.d4? handles 1…Qc3 by shutting the long diagonal, so that 2.Qh6 cannot be countered by the unpinned black queen. But 1…Qc2! refutes the try. The key 1.d3! (waiting) closes two lines in anticipation of the black queen’s release. Now 1…Qc3 is answered by the changed mate 2.Qh1 (2…Qf3 prevented), while 1…Qc2 allows the transferred mate, 2.Qh6 (2…Qg6 prevented). The remaining variations are as set: 1…Qc4+ 2.Qxc4, 1…Qxc1 2.Rxc1, 1…b5 2.Qxc5, and 1…Kb5 2.Bd7 (pin-mate).

Jacob Hoover: The “Girl Power” theme strikes again (four out of the six variations feature queen mates)!

272. Alex Boudantzev
The Australian Problemist 1962
Mate in 2

The fairly easy key 1.e4! threatens 2.Bd5. Black has two en passant capture defences that involve some curious line effects. 1…dxe3 e.p. interferes with the f2-bishop and permits 2.Sd4; this illustrates the only way by which a line-closing interference can result from a capturing move, possible since the capture square e3 is initially empty. 1…fxe3 e.p. likewise cuts off the bishop but the removal of the key-pawn has opened the fourth rank for the black queen, which stops the knight mate; White instead plays 2.Qxc7, exploiting the opening of the diagonal controlled by the g3-bishop. En passant play occurs in two more variations, 1…d5 2.cxd6 e.p. and 1…b5+ 2.cxb6 e.p., in which the thematic captures are executed by White to deliver two battery mates.

Andy Sag: En passant theme – very cute! We could add a black knight on h7 for a fifth variation, 1…Sf6 2.Se7.
Jacob Hoover: Quite the interesting idea, and it was an idea very clearly demonstrated, with no by-play to distract the solver.

273. Alexander Goldstein
Holland vs. Poland Composing Match 1937
1st-2nd Prize =
Mate in 2

Random moves by the d7-knight would threaten 2.Qd8, but they are defeated by 1…Bd6/Be7. The key 1.Sc5! ensures that the bishop refutations are not playable. Now Black has four defences against the threat, including three flight-taking moves, and they are all answered by battery mates delivered by the f7-knight. 1…Sxd5/Sd7 (enabling the a5-bishop to guard d8) 2.Sd6, 1…Ke7 2.Sxh8, 1…Kf8 2.Sxg5, and 1…0-0 2.Sxh6. Remarkably, the knight fires the batteries from four different directions, i.e. it activates four white line-pieces in turn – a maximum task achievement.

Andy Sag: The key adds two flights, including castling, and leaves the white queen en prise.
Jacob Hoover: Nice one, not only due to the battery-play theme, but also because there’s no distracting by-play.

This two-mover was selected from Chess Problems: Tasks and Records, a book by Sir Jeremy Morse. Sadly, this British composer and world authority on task problems has passed away, at the age of 87. A comprehensive article on the Life and Work of Sir Jeremy Morse can be found on the British Chess Problem Society site.

274. William Whyatt
problem 1957
Mate in 3

In the initial position, set play is arranged for every possible black move. 1…Bd~ 2.Sh7 (threat: 3.Bxg5) Bxd2 3.Qh1 and 1…Be~ 2.Bxf7 (threat: 3.Qxg6) Bc2 3.Qh1. White takes advantage of the fact that Black cannot afford to move both bishops without permitting Qh1 mate. But White has no way of preserving these variations, e.g. 1.Kc7? Bxd2! 2.Bxf7 Bf4+. (Incidentally, can you work out why 1.Ke8 isn’t technically a try? That is, what are the various black moves that would defeat it?) The key 1.Sd7! (waiting) abandons the set play and replaces it with 1…Bd~ 2.Bb4 (threat: 3.Bf8) Bxb4 3.Qh1 and 1…Be~ 2.Se5 (threat: 3.Sxf7) Bb3 3.Qh1. This is a three-move mutate, an uncommon form in which the late William Whyatt excelled.

Jacob Hoover: A very clever three-mover mutate.
Andy Sag: A tale of two bishops!

275. David Shire
Australian Chess 2003
Helpmate in 2
Twin (b) WRc8

The diagram position is solved by 1.Bd5 Be3 2.Kd3 Bf5. Black’s bishop move to d5 interferes with the white rook and gives the black king access to d3. White’s bishop move to e3 cuts off the black rook (besides covering two flights), an interference required for the eventual pin-mate delivered by the other white bishop. Position (b) has a white rook starting on c8, and this changes the solution to 1.Re3 Rd5 2.Kf4 Rxc4. Here Black’s rook move to e3 closes a white bishop line and enables the black king to reach f4. White’s rook move to d5 interferes with the black bishop (besides controlling the fifth rank), ensuring that Black cannot stop the pin-mate given by the other white rook. Two fabulous pairs of mutual interference between pieces of different colours, or a double bi-coloured Grimshaw.

Andy Sag: Not as hard as Feather’s No.269. In each case, Black blocks a white line then White blocks a black line; next the black king moves to self-pin the piece that first moved, then the white piece from c8 can mate. Nice twin.
Michael McDowell: I enjoyed David Shire's anticipatory self-pin helpmate, but I think a small improvement is possible. In both solutions White's first move interferes with a black piece. In (b) there are two ways of setting up a mate, but 1.Re3 Rc5 2.Kf4 Rd4 fails because of the lack of an interference. In (a) there is no choice, as 1…Be3 is the only safe way to guard d4 and d2, so the interference is incidental. If a white pawn at b2 replaced the black pawn at c3, the option of 1…Bc3 would make 1…Be3 a genuine choice. The gain in thematic unity seems to me to justify the use of the white pawn.