Weekly Problems 2017-B

Set mates are provided for all of Black’s moves in the diagram: 1…B~ 2.Se6, 1…Bxd4+ 2.exd4, 1…Sa~ 2.Qb5, 1…Sc2+ 2.Rxc2, and 1…Sb~ 2.Rc6. Waiting tries include 1.Kb2? Sc4+!, 1.Rd1? Sc2+, and 1.Rb2? Bxd4! The key 1.Qe6! (waiting) blocks e6 but vacates b3, and additionally the queen unguards b4 and b5 while taking control of d6 and c6. Four changed mates result in this fine mutate. 1…B~ 2.Sb3, 1…Bd6 2.Qxd6 (an extra bishop correction not seen in the set play), 1…Bxd4+ 2.exd4, 1…Sa~ 2.Rb5, 1…Sc2+ 2.Rxc2, and 1…Sb~ 2.Qc6.

Andy Sag: Complete block with six variations including four changed mates and two set cross-checks. The a2-pawn prevents a cook: 1.Ka2, and the f3-pawn prevents another: 1.Qb4+ Kd5 2.Bg2.
Ian Shanahan: Good pendulum key – a device favoured by this composer, as I recall – leading to symmetrical mate-changes.
George Meldrum: I found this difficult to solve. Maybe it was the fact that all the mates were changed from set play (apart from the checks on the white king). Or maybe it was the new mate after 1…Bd6.
Nigel Nettheim: Neat though fairly modest.

The set play consists of a short sequence, 1…Kd8 2.Rg8 Se6. When Black commences, the solution is extended to three moves: 1.Ke7+ Kc7 2.Kf8+ Kd8 3.Rg8 Se6. Of the many possible switchbacks, Black must choose Ke7-f8 to temporarily close the seventh rank and enable 1…Kc7 for White. Part (b) is solved by 1.Rg7 Ng4 2.Kf7+ Kd7 3.Rf8 Sh6. Now it’s the white knight that makes a switchback, and only Ng4-h6 works as the alternatives would disrupt Black’s play.

Andy Sag: A tale of two switchbacks; black king in (a) and white knight in (b).
Jacob Hoover: In part (a), notice how the last move-and-a-half exactly equals the set play. Part (b) has similar play with a black battery play assisting in setting up the mating position, which, unlike (a), is not a model mate. A rather interesting miniature indeed.
George Meldrum: The checks, the tempo thing – just a pleasure.
Ian Shanahan: The tempo in (a) leading again to the set play is sweet, as is in (b) Black's follow-my-leader and White's switchback. Overall, a fine problem that should have been in that year's award.

The sacrificial key 1.Bxb5! vacates a6 to threaten 2.Ra6. If 1…Bxb5 the self-block permits White’s B + R battery to open with 2.Rd4, shutting off the black rook. Any move of the latter piece defends by pinning the e6-rook, and a random move along the d-file, 1…R~, allows the white queen to guard b5 for 2.Ra4. If 1…Rc5/Rxe5, losing control of the d2-bishop, then 2.Rxb3. And the correction 1…Rxb5 – accepting the initial sacrifice again – is a self-pin that generates a fourth battery mate, 2.Rxc4. The black rook creates one more variation with 1…Rd8+ 2.exd8=Q. The by-play makes further use of the white queen: 1…Qg6 2.Qc7 and 1…Rh6 2.Qa1.

Andy Sag: There are seven defensive variations. Four defences allow battery mates with different moves of the b4-rook. The other three defences produce set queen mates (one promoted).
Ian Shanahan: Masked batteries by both Black and White. Pins galore! Beautiful…
Nigel Nettheim: A good set of mates with the b4-rook.
Jacob Hoover: This was a nice one with the battery plays, and I also liked that all of the by-play variations are set.
George Meldrum: Eyes are drawn to the centre of the board with Black twirling the rook around in hammer throw action style. Particularly like the lines after the rook or bishop capture on b5.

The first part of this miniature is solved by 1.d5 Bd6 2.Rc6 Be5 3.Kc5 Kc3 4.Qd6 Bd4, and part (b) by 1.Rc8 Kd3 2.Kc7 Kc4 3.Rb7 Kc5 4.Qd8 Bd5. The two final positions are ideal mates and exact echoes of each other. The twinning shifts the white king to e3 but paradoxically the piece immediately moves back to d3. The composer indicated that a two-solution setting is possible with the white bishop starting on e7, but preferred the twin; the latter arrangement obliges the solver to work out why the solution of (b) wouldn’t work in (a), despite how the king is already “correctly” placed on d3.

Andy Sag: The first task is to find a self-block pattern where a king and bishop can mate. The pawn plays a vital role to ensure an unguarded square for the bishop.
Nigel Nettheim: In (a) c3 is well-guarded, but the white king is shepherded to it. In (b) the d4 route to c5 is tempting for the white king, but those black squares are too well-guarded so he tip-toes around on the white squares. Very clever.
Jacob Hoover: The numerous interferences and the echo mates made this one a very rewarding solve. I must confess, however, that I actually solved part (b) before I could even see how to solve part (a).
George Meldrum: Amazing how the problem and its twin have the same structure in the solution on two parts of the board with the initial setting so similar.

The key 1.Qg2! forces the two half-pinned knights to deal with the threat of 2.Qa2. When either knight moves, the other is left pinned and this weakness is exploited in every variation: 1…Sc3 2.Qxc6, 1…Sb4 2.Qe4, 1…Sc5 2.Qc2, and 1…Sd4 2.Rc3. Good that the thematic play is evenly shared by the two black pieces.

Andy Sag: A Meredith setting with half-pinned knights. In three of the mates, the queen takes up a position opposite and on the same rank or file as the defending knight. The fourth one is a self-block where the rook mates. All four are pin-mates.
Nigel Nettheim: The somewhat symmetrical attempt 1.Qa8? (2.Qa6) is answered by 1…Sc5 or 1…Sb4 because the queen is too hemmed-in on a8. The setting seems very economical.
Jacob Hoover: It was nice seeing a problem with a half-pin setting and also no distracting by-play.
Ian Shanahan: A complete black half-pin. Charming.
George Meldrum: This problem has an attractive setting but is not a heavy hitter in the key move and threat department. The motive of the composer is clear in the variations where the knights play to b4, c3, and c5. Here we end up with a neat recurring mating pattern of queen, king, and knight in a straight line.

The square-vacating key 1.Qa6! grants a flight on d4 and threatens the double-check 2.Sc4. Any black move to d4 would defeat the threat, and four such defences err by opening white lines, besides blocking the flight. 1…Sfd4 2.Sf7 and 1…Rd4 2.Rf5 see White exploiting the opened lines of guard. In 1…Scd4 2.Qd6 and 1…d4 2.Qb5, White makes use of the lines directly in the mating move. Black plays twice more to d4 with the unguard 1…Qd4 2.Sg6 and the flight-taking 1…Kd4 2.Sd1. So an impressive total of six defences take place on the same square.

Andy Sag: The key stops 1…Rxa1, gives a flight and threatens double-check mate defendable by moving any of six pieces to d4. Four of these open lines to allow different mates; moving the queen unguards g6 and taking the flight unleashes the battery mate.
Nigel Nettheim: 1…dxc4 is unprovided, and the white queen escapes capture by means of the key, which is therefore not a strong point. As compensation, or more, the six occupations of d4 that prevent a double-check lead to nice variations.
George Meldrum: The position is ugly, I love it! The queen moves away from the centre of play and gives the black king a flight square. Bravo to the key move, and to the black hole on d4 to which dark matter is drawn.
Ian Shanahan: A “trying” problem! Clearly the white queen has to move (to avoid 1…dxc4), but where? A fine composition, with lots of intensive strategic line-play and an excellent flight-giving key by a famous Australian duo.
Jacob Hoover: The fact that all of the defences happen on the same square – even the by-play variations! – gives a high degree of unification to this problem.

The key 1.Qh7! threatens 2.Qd3+ c4 3.Qxc4. Black's thematic units are the knights and c5-pawn, each of which prevents two of three potential mates: Sc7, Sd4, and Rxb4. When one of these black units moves to answer the threat, it unguards two mating squares, and White responds by checking on the third square that is still guarded twice. The check deflects the other two black defenders, forcing each to leave one mating square completely unprotected. 1…c4 2.Sc7+ [A] Sexc7 3. Sd4 [B] or 2…Sdxc7 3. Rxb4 [C]. 1…Sdf4 2.Sd4+ [B] cxd4 3.Rxb4 [C] or 2…Sxd4 3.Sc7 [A]. 1…Sef4 2.Rxb4+ [C] Sxb4 3.Sc7 [A] or 2…cxb4 3.Sd4 [B]. The recurrence of three white moves as second-move continuations and third-move mates produces a cyclic pattern. Specifically, this outstanding three-mover exemplifies cyclic overload.

Andy Sag: Black looks safe with the c5-pawn and two knights providing double guards on c7, d4 and b4 but one of these must move to defend the threat, allowing White to exploit the resulting overloading of defenders.
Jacob Hoover: Each of Black's three defences unguards two of three mating squares and in each case White decoys another guard with a sacrifice on the third square.

The key 1.Qxb6! carries a threat, 2.Qxe6, which is met by any black knight move. The thematic piece causes two pairs of self-interferences with the rooks: 1…Sd4 2.Bxb4, 1…Sf4 2.Bxh4 (set 2.Qxh4), 1…Sd8 2.c8=S, and 1…Sf8 2.g8=S. Another two interferences which cut off the queen and bishop occur with 1…Sc5 2.Qd6 and 1…Sg5 2.Qf6. And two square-clearances result from capturing the pawns: 1…Sxc7 2.Qxc7 and 1…Sxg7 2.Rxg7. So a knight-wheel is produced. The by-play repeats a queen mate: 1…Qd6 2.Qxd6.

Jacob Hoover: Since we have eight possible knight moves and eight different mates, this is a knight-wheel.
Andy Sag: A classic knight-wheel with four symmetrical pairs of variations.
George Meldrum: At first sight Black’s defence looks rock solid. When scanning Black’s moves, the knight allows White to mate for all moves other that when moving to c5, c7 or g5. The knight hence draws attention to itself and helps the solver find the solution.
Ian Shanahan: A complete black knight-wheel. However, the symmetry here detracts, and the white force is rather strong for the effects shown.

The black king has two flights on g2 and e3, both unprovided. There is a set variation for the e5-pawn – 1…exd4 2.Sxf2 – but the key captures that pawn to remove its control of the B + S battery: 1.dxe5! (waiting). Now 1…Kg2 enables 2.Sxf2 while 1…Ke3 self-pins the black bishop and allows the vertical R + S battery to operate: 2.Sd4. A random black bishop move that unguards d4, namely 1…Bd4/Bxe1, also permits 2.Sd4. Four corrections by the bishop generate a further mix of direct and indirect battery mates: 1…Bxg3 2.S4xg3, 1…Bxc5 2.Sxc5, 1…Be3 2.Sf2, and 1…Bxg1 2.Sxg1. The try 1.Kxe5? (waiting) leads to one changed mate, 1…Bxe1 2.Sf6, but 1…Ke3! refutes. The severely underused white queen could be replaced by a black pawn on g4, with no difference to the play except for the loss of the aforementioned set line, 1…exd4 2.Sxf2.

George Meldrum: The key move rids the pesky black pawn on e5, and vacates the d4-square needed for the knight in one of the variations. A number of reasonable looking first moves for White make the solution harder to find.
Andy Sag: Compact setting. The key leaves eight legal moves for Black, all answered by knight moves, mostly battery mates. The flight self-pins the bishop; I like that one!
Jacob Hoover: The king-flights 1…Ke3 and 1…Kg2 allow 2.Sd4 and 2.Sxf2, respectively; while these moves look like repeats of previously seen mates, they could be viewed as distinct mates because the king is mated on a different square.
Ian Shanahan: Finding the key took a long time. Batteries galore! However, the position is rather cramped and ugly – which seems to be a feature of Roberts' style.

The thematic key 1.Qd7! (threat: 2.Qxd6) unpins the black knight, which in turn pins the white queen by opening the diagonal for the f5-bishop. A random move by the knight loses control of the R + P battery: 1…S~ 2.b6. The knight has three correction moves, two of which unpin the white knight on c4: 1…Sc7 also interferes with the d8-bishop and allows 2.Sb6, while 1…Sc5 also self-blocks and enables 2.Se3. The third correction 1…Sd4 cuts off the black queen for 2.Re5 (which also follows 1…Qe5). The by-play consists of 1…Qxc4+ 2.dxc4, 1…Sxd7 2.b8=Q, and 1…Bc7/Be7 2.Se7.

Andy Sag: The sacrificial key unpins the e6-knight which then moves to pin the white queen. Knight moves to the c-file unpin the c4-knight. 1…Sd4 unguards e5 allowing a pin-mate. Other knight moves unleash battery mates. A great example of pins and unpins.
Ian Shanahan: Strategically, incredibly rich. The unpinning key, moves by the unpinned knight, and ensuing mates, show one of my own favourite themes – the Dalton II theme (also known as the Plant theme). This unpinned black knight also makes correction moves which unpin a white knight, harking back to the strategic fireworks of the Good Companions. So: an unpin-pin-unpin sequence.
George Meldrum: The setting appears to contain some froth, but the main lines of play initiated by the black knight on e6 produce some beautiful mates by White.

Black has two legal moves in the diagram, one with a set continuation: 1…d5 2.Kxd7 d4 3.Rc5. White must provide for the other black move, 1…Kd5, and remarkably the only way is 1.Bg2!, setting up a B + P battery. Now 1…Kd5 is answered by the sacrifice 2.Re3, which branches to 2…fxe3 3.f4 and 2…Kc6 3.Se7. The other variation is unchanged from the set play: 1…d5 2.Kxd7 d4 3.Rc5.

Andy Sag: It took a bit of lateral thinking to work out how to deal with the unprovided flight. The rook sacrifice on second move is a clever touch made possible by the key setting up a hidden battery.
Jacob Hoover: Battery-creating key.
George Meldrum: The a4-pawn suggests that the black king will wander towards it, and the white bishop on f1 looks unneeded – paltry clues to help unravel this puzzle. Very difficult to solve and requires an “aha” moment for the idea to surface. Wonderful key move.

There’s thematic set play based on moves by the f3-bishop and b5-knight that open white lines of guard: 1…Bf~ 2.Sg6 (white rook controls f7) and 1…Sb~ 2.Bf8 (white bishop controls e8). The key 1.Sd6! observes f7 and e8 but removes a guard on f6 and d7 (the latter by cutting off the white queen). When the f3-bishop and b5-knight move to stop the threat of 2.Sc8, they again open white lines of guard, but changed mates result: 1…Bb7 2.Bf8 (white rook controls f6) and 1…Sa7 2.Sg6 (white bishop controls d7). Hence we see a reciprocal change of mates compared with the set 1…Bb7 2.Sg6 and 1…Sa7 2.Bf8. Two other variations are 1…Sxd6 2.cxd6 and 1…Rxg8 2.hxg8=S.

Andy Sag: It is clear that the knight must vacate e8 to guard that square if 1…Rxg8. Two defences open lines to d7 and f6 respectively.
George Meldrum: The mates following 1…Sa7 and 1…Bb7 are swapped around after the key which is kind of cute.
Ian Shanahan: There are only four variations I can see, but rich line effects. After 1…Bb7 and 1…Sa7 there is a reciprocal change between set and post-key play involving the mates 2.Bf8 and 2.Sg6. Pretty, despite the fairly heavy position.

The white knight takes two moves to reach c5 or f2 where it can check and regain control of the d3-flight, and this would be mate if Black were to self-block on f5 and f4. After 1.exf5, White avoids 1…Sxh3? because then 2.Sgf4 would check while 2.Shf4 would pin the white knight; so 1…Se6 2.Shf4 – not 2.Sgf4? again pinning the white knight – and 2…Sc5. The second solution begins with 1.Bxf5, and similar White and Black dual avoidances follow: 1…Sh3 – not 1…Sxe6? – 2.Sgf4 – not 2.Shf4? – and 2…Sf2.

Andy Sag: Two symmetrical solutions where pin avoidance determines which black knight moves to f4.
Jacob Hoover: This one was pretty easy; I had it solved about one minute after initially seeing it.
George Meldrum: Easy to solve but very elegant.
Nigel Nettheim: Not hard to solve, but neat sequences with nice symmetry. The d5-pawn has been added to prevent a third (quite nice but non-thematic) solution: 1.Kxf5 Rf3 2.Kf6 Sd5.
Ian Shanahan: Model mates, perfectly echoed strategy (including pin avoidance at Black’s second move). Beautiful!

The key 1.Bb3! yields a flight on g6 in addition to the one on e6. The threat 2.Sf4, utilising the new B + S battery, would unpin the f3-rook. Anticipating the unpin, 1…Bb4 defends but the black bishop has interfered with the queen pinned on b7, allowing White to unpin it with 2.Sde7. The self-block 1…Rg6 is answered by the shut-off 2.Sf6. Another battery mate follows 1…Ke6, when 2.Sb6 shuts off the unpinned queen. The other flight 1…Kg6 provokes 2.Sxe5. Lastly, 1…Rf6 also anticipates the unpin of the black rook and it gives 2.Rxf6.

Andy Sag: Key provides for the set flight but adds a second flight and sets up a battery. The bishop defence is interesting; it exposes the battery bishop to the f3-rook which would be unpinned by the threat but shields it from the queen which can then be unpinned instead.
Brian Stephenson: The white pawns on the king-side suggest that the black king will be allowed to g6, and this suggests the key.
Nigel Nettheim: Not a pretty picture, largely because the c3-bishop had to be almost immobilized by four black pawns. But that was worthwhile, for the scheme is very intricate, with the battering bishop attacked separately along the rank and file: 1…Bb4 2.Sf4? 2.Sde7! and 1…Ke6 2.Sf6? 2.Sb6!
Jacob Hoover: 1…Bb4 2.Sde7 features a Goethart unpin (the unpin is achieved by interposing on the pinning line).
George Meldrum: The key move allows another king flight. The five variations require concentration and are a delight.
Ian Shanahan: The position is ugly, and there is an unprovided flight. But the strategy is very rich. 1…Bb4 defeats the threat (which would unpin the black rook), but interferes with the pinned black queen which can now be safely unpinned: 2.Sde7. This shows what is known as “form and antiform”. Strategically, we see the Goethart and anti-Goethart themes.

The key 1.Se5! grants a flight on e5 but removes one on f7. Now the black king has three legal moves, all of which stop the threat of 2.Qxd6, and in each case a pin-mate follows: 1…Kxe5 2.Bxf3, 1…Kd5 2.Bc4 (a change from the set 2.Bxf3), and 1…Ke7 2.Re8. The black knight on d6 is hence pinned on three different lines by the queen, d8-rook, and c5-bishop. The same knight defends with any move and a random placement 1…Sd~ enables 2.Sg5. Two correction moves prevent 2.Sg5 but they produce self-interferences: 1…Sf7 2.Sxf8 and 1…Se4 2.Bc4. This first-class composition, finely constructed with no white pawns, was selected for the FIDE Album.

Andy Sag: Sacrificial give-and-take key provides for 1…Ke7. All three flights result in pin-mates.
George Meldrum: White must stop the black king from moving to f7 as flights to the g-file are unstoppable. This makes finding White’s first move easier, but what a move! On all three black king moves the knight on d6 is pinned. The variations where the knight moves to f7 and e4 causing self-interferences are sweet.
Nigel Nettheim: 1…Kf7 can’t be allowed, which suggests the key. Self-pin is the name of the game. All three pinning lines are opened simultaneously by 1…Sd~. Very satisfying.
Ian Shanahan: Absolutely beautiful! On the down side, there are unprovided flights. The sacrificial key is give-and-take. What happens then is spectacular: the d6-knight is pinned from three directions after the king flights; the d6-knight makes a random move and two corrections. Wonderful!

In a full-length and dual-free set variation, White advances the king to guard g6 and induces the h5-pawn to open the h-file for the rook: 1…h4 2.Kg4 h3 3.Kf5 hxg2 4.Bxg7+ Kxg7 5.h8=Q. If White attempts to preserve this variation with 1.Rh1?, then 1…h4 2.Kg4 h3 3.Kf5 h2! refutes. The surprising key 1.Bc5! targets the g1-square as part of a new plan: 1…h4 2.Kg4 h3 3.Bg1 hxg2 4.Rh6 gxh6 5.Bd4. In contrast to the bishop sacrifice of the set play, White sacrifices the rook instead and mates with the bishop.

Andy Sag: A tricky one-liner with a very busy bishop and a timely forced rook sacrifice.
George Meldrum: A different solution can be found if you allow Black to move first. This is a solver’s problem, difficult, and with an unexpected outcome which is delightful.
Nigel Nettheim: The tempting set-play cannot be maintained, so White finds an ingenious alternative way to make use of zugzwang. This is a very well-contrived composition. The d-pawns can only be on that file. I think the g5-pawn is only there to make the set play a unique line and thus really tempting; that is important and increases the difficulty.
Ian Shanahan: A hard nut to crack. The goal is to put something on g1 to blockade the advancing pawn while avoiding stalemate. A stunning line – White brings a bishop out of the fray completely and sacrifices a rook. The set play makes the problem a rare example of the more-mover mutate!

The thematic key 1.Se3! concedes a flight and threatens 2.Sf5. The white knight is placed where it can be captured by five black units, and they all provoke different mates. 1…Rfxe3 opens a white queen line to e4 and allows 2.Se6, which removes the e8-rook’s guard of that square. Similarly 1…Rexe3 gives the f1-bishop control of c4 and leads to 2.Sc6, when the c7-rook’s line to that square is closed. 1…fxe3 is a plain self-block that enables 2.Bc3. White exploits an unguard along the g-file with 1…Qxe3 2.Qg7. Lastly, the flight-taking 1…Kxe3 is answered by 2.Bc5.

Jacob Hoover: The key sacrifices the knight to no less than five black units.
Andy Sag: The key invites a flight-capture. All five variations must remove the key-piece to defend threat. The queen mate and a pair of knight mates are set play. The key adds a pair of bishop mates.
Brian Stephenson: The general self-block error (by 1…fxe3) is met by 2.Bc3 and then Black corrects by capturing instead with the rooks and the queen, each of which protects c3.
Nigel Nettheim: A wonderful and clean five-way sacrifice.
Ian Shanahan: The most spectacular variations involve captures of the knight by the two black rooks: each opens a white line, allowing White to close another white line in the mate – one of the Russian line-themes (Theme B or Somov).
George Meldrum: The timing of this problem to the anniversary of the Battle of Beersheba did not go unnoticed! The white horse moves to a square where it threatens mate, yet it can be taken five ways. Black rooks capture on e3, open lines, allowing the remaining steed to finish the battle. 

[Editor: The appearance of this problem a few days before the 100th anniversary of the Battle of Beersheba – involving the Australian light horse regiments – was in fact accidental. What an amazing coincidence!]

The Banny theme is a reversal sequence in which two try-moves [1.A? and 1.B?] and their refutations [1…a! and 1…b!] reappear after the key (or after a further try) in two variations as the defences [1…a and 1…b] and resulting mates [2.B and 2.A]. This problem shows the theme twice and also contains, for each Banny sequence, a preliminary try that is refuted by both thematic black moves. The first group of phases (four tries) utilises the d5-rook with the queen mating from h1. 1.Rd2? (threat: 2.Qh1), but 1…Rxb3! [a], 1…Ra4! [b]. 1.Rd4? [A] (2.Qh1), 1…Ba2 2.Qxc2, but 1…Rxb3! [a]. 1.Rd3? [B] (2.Qh1), but 1…Ra4! [b]. 1.Qh1? (2.Rd4/Rd3/Rd2/Rd1), 1…Rxb3 [a] 2.Rd3 [B], 1…Ra4 [b] 2.Rd4 [A], 1…Ba2 2.Rd1, but 1…c1=Q! The second group of phases (three tries and the key) utilises the d6-bishop with the queen mating from h6. 1.Bg3? (2.Qh6), but 1…h1=Q! [c], 1…Qxb2! [d]. 1.Be5? [C] (2.Qh6), but 1…h1=Q! [c]. 1.Bxh2? [D] (2.Qh6), but 1…Qxb2! [d]. 1.Qh6! (2.Be5/Bf4/Bg3/Bxh2), 1…h1=Q [c] 2.Bh2 [D], 1…Qxb2 [d] 2.Be5 [C], 1…c1=Q 2.Bf4. Total change between the virtual and actual play. This is a fine example of modern pattern play in which certain moves recur in different parts of the solution but with their functions changed.

Composer: The Banny theme-pattern, doubled. This task can be achieved more economically: I have done it with 14 units!
Andy Sag: The key sets up a battery with a quadruple threat. There are three defences, each requiring a different bishop move.
Jacob Hoover: The three defences force particular bishop moves. However, there's no defence that forces 2.Bg3, so this is an incomplete Fleck.
George Meldrum: A try-try, try-again problem. The best try is 1.Qh1?, and more with 1.Rd4?, 1.Rd3?, 1.Be5?, and 1.Bxh2? Very tricky.

If 1.c4?, threatening 2.Qxb5, then 1…Qf3!, and if 1.Sc4?, threatening 2.Sb6, then 1…Qe3! The key 1.Qd5!, with the threat of 2.Qb3+ Qxb3 3.cxb3, induces the black rooks to obstruct the queen on the third rank. 1…R4g3 2.c4 (3.Qxb5) bxc4 3.Qxd7; White avoids 2.Sc4? because of 2…Qxe6!, revealing that the rook defence has also opened a diagonal for the queen. Similarly, 1…R2g3 2.Sc4 (3.Sb6) bxc4 3.Qxd7; not 2.c4? here since the black queen could still access the long diagonal with 2…Qg2/Qh1! The subtle differentiation between 2.c4 and 2.Sc4 (dual avoidance) is skilfully arranged. There’s by-play with 1…Qf3 2.Sxf3 and 3.Qb3.

Jacob Hoover: The key preserves the set play which involves the black rooks interfering with the black queen.
George Meldrum: The black rooks move to g3 to defend against the threat, but in turn block the passage of the black queen defending against White’s two threats on c4. A neat self-interference pattern.
Andy Sag: The key creates a decisive threat and is easy to spot as the black queen has no safe pinning move. The rook defences restrict the black queen in different ways, allowing one of the first move try continuations to succeed on second move. A white pawn on h2 would keep the pinning defence dual free.

In the initial position, the f8-bishop and a6-rook prevent knight mates on c5 and f6 respectively, while 1…Sg4 2.Qxf3 and 1…g4 2.Rf4 are also set. The Novotny try 1.Bd6? threatens the knight mates – separated by 1…Rxd6 2.Sxc5 and 1…Bxd6 2.Sxf6 – but because the try-bishop has cut off the d8-rook, 1…Sg4! refutes (2.Qxf3+ Kxd4). Likewise, 1.Rd6? entails the Novotny threats which are similarly separated, and now 1…g4! refutes because the try-rook has interfered with the b8-bishop (2.Rf4+ Kxf4). A white Grimshaw is thus brought about. Two further tries are 1.dxc5? (2.Qd4/Rd4) Bxc5 2.Sxc5 but 1…Rd6!, and 1.Rxf6? (2.Bf5) Rxf6 2.Sxf6 but 1…Bd6!; here the first-move obstructions of the knights’ mating squares stop White from exploiting Black’s interferences on d6. White avoids all of the self-hindrances with 1.Kd1!, which threatens 2.Qe1. Black defends by shutting off the d8-rook, and a Grimshaw results: 1…Rd6 2.Sxc5 and 1…Bd6 2.Sxf6. Also, 1…Sg4/Sf1 2.Qxf3 and 1…g4 2.Rf4 occur as set. This two-mover by the late Russian Grandmaster must be one of the best ever Chess in Australia original. The Novotny theme is combined with white and black Grimshaws, and the four thematic defences in the post-key play also act as the refutations of the four main tries.

Andy Sag: The innocuous king key creates a threat that can only be defended by giving the king an escape. All four defences are set play.
George Meldrum: This noisy problem obscures the quiet key move and threat. Clever responses to White placing a rook or bishop on d6 are a good diversion.
Ian Shanahan: More Russian line-themes and tries. All the action takes place on d6 – black and white Grimshaw and Novotny.

All black moves in the diagram are provided with set mates, and the only way to preserve them all is to play 1.Bh8! (waiting). 1…a2 2.Sb2, 1…exf3 2.Qxd3, 1…Sf~ 2.Sxd2, 1…Sc~ 2.Se5 (dual 1…Sb4 2.Se5/Rc3), 1…Be6 2.Qxe6, 1…Bf7 2.Qxf7, and 1…Bg8 2.Qxg8. Other moves by the a1-bishop fail as they would disrupt the set play: 1.Bb2? a2!, 1.Bc3? exf3!, 1.Bd4? Sxe3!, 1.Be5? Sc~!, 1.Bf6? Be6!, and 1.Bg7? Bg8! The self-obstructions caused by the tries and the avoidance of such by the key exemplify white safety play. Remarkably, we also find four connected tries by the white queen, which cannot maintain control of its four mating squares: 1.Qf5? Bg8!, 1.Qh7? Be6!, 1.Qg4? Bf7!, and 1.Qe8? exf3!

Jacob Hoover: Every black move in the diagram has a mate set against it, and only 1.Bh8! preserves this block.
Andy Sag: Lots of bishop tries and queen tries. Complete block setting and the bishop must go the full distance to avoid messing it up.
Ian Shanahan: An astonishing corner-to-corner key. If the bishop stops anywhere else, White is obstructed somehow. I was hoping for some changed mates, but the key simply preserves the block.
George Meldrum: The bishop moves to the far-off corner, still tempted to stop at any of six points in the travel. The lure to shorten the travel is responded to by singular and subtle responses by the dark side. This scene yields an entertaining journey.

The key 1.Be3!, by controlling f4, threatens 2.Qg8+ Ke4 3.Qe6. The self-block 1…Bxd6 leads to 2.Sb6+ Ke5 3.Bd4, which is a model mate. Another self-block, 1…Bxc4, is answered by 2.Qf5+ Kxd6 3.Bc5, also a model mate. The 1…Bxd6 variation shows a change from the set 2.Se3+ Ke5 3.Bd4/Qf5 (dual).

George Meldrum: Nice first move taking away the ability for the white pawn to move.
Andy Sag: Further set play is 1…Bb3 2.Qf5+ Kxc4 3.Qc5 but duals with threat in the post-key play. Once I saw that 1…Bxc4 (threatening 2…Ba6+) could be answered by set play, I looked for a key that posed a threat that was defended by that move. The changed play after 1…Bxd6 was a bonus.
Jacob Hoover: The two defences lead to echoing model mates.

In the set play, the black rook cannot maintain its focus on the two mating squares of the a4-knight: 1…R~file 2.Sxb6 and 1…R~rank 2.Sc3. No white moves could preserve the block, however, e.g. 1.Bg1? Rc2+!, 1.Kxh3? Rh6+! The sacrificial key 1.Bc5! (waiting) unguards c5 but controls d6, freeing the e8-knight to mate instead: 1…R~file 2.Sf6 and 1…R~rank 2.Sc7. The correction 1…Rxc5 brings back 2.Sxb6, while 1…bxc5 results in a transferred mate, 2.Sc3. Because 1…Rc5 2.Sxb6 is set, the post-key 1…Rxc5 2.Sxb6 doesn’t involve a mate transference, so we don’t have the full Rukhlis theme (which requires two changed and two transferred mates). Regardless, this is an excellent mutate with changed focal play.

Andy Sag: Waiter with changed mates but some duals.
George Meldrum: Simple and sweet.
Jacob Hoover: This is probably one of the most clever mutates I've ever seen.
Ian Shanahan: I know this problem well indeed! It inspired me to produce similar things. Focal theme, pendulum key, and (nearly) the Rukhlis theme. Macleod was a Grandmaster who well and truly deserved the title.

The diagram is an incomplete block position with set play arranged for all of Black’s moves except 1…e5 and 1…Sb6. The key 1.Rf8! (waiting) completes the block by preparing the rook to attack on the d-file: 1…e5 (self-block) 2.Qc4+ Kd6 3.Rd8 and 1…Sb6 2.Rd8+ Sd7 3.Rxd7. Three more self-blocking defences lead to play unchanged from the set: 1…Sd6 2.Sc7+ Kc5 3.Qe3, 1…Sc6 2.Sc7+ Kc5 3.Sd7, and 1…Sb5 2.Sxb4+ Kc5 3.Sd7. Lastly, 1…exf6 2.Rd8+ Sd6 3.Rxd6 shows a concurrent change from the set 2.Rd7+.

Andy Sag: Black has six legal moves, four with set play. The key changes one set play, preserves the other three and provides for the remaining two.
Jacob Hoover: I liked the 1…Sc6 and 1…Sb5 lines in particular, in which the a7-knight makes a move and then the a6-knight moves to stay adjacent to it.

The thematic key 1.Se4!, besides granting a flight on e4, unpins the f3-knight which could give various discovered checks. The threat is 2.Rc5. A random defence by the black knight loses control of the R + S battery on the d-file: 1…Sf~+ 2.Sf5. Two correction moves by the knight enable White to fire the B + S battery: 1…Sxd4+ (self-pin) 2.Sf2 and 1…Se5+ (self-block) 2.Sf6. If the black king takes the flight, White activates the Q + R battery: 1…Kxe4 2.Re6. The by-play consists of 1…Bxc6 2.Qxc6 and 1…Qxb7 2.Sxc3. So there are five battery mates, including the threat. The d7-bishop may be replaced by a black pawn.

Andy Sag: The sacrificial key unpins the f3-knight, allowing it to unleash battery checks and opens the a3 to f8 diagonal, permitting queen checks which, however, do not defend against the threat. A busy problem with an assortment of batteries, unpin and re-pin, and double-checks.
Jacob Hoover: This was way too easy; I almost immediately recognized the potential for a black battery play and looked for an unpinning move to make such a battery play possible.
Nigel Nettheim: Fine play against the f3-knight checks, and four batteries altogether. (If the e1-rook were on e2, a mate cannot be provided for 1…Se1+.)
Ian Shanahan: A brilliant (if, knowing Mansfield's work, obvious!) self-sacrificing key, giving a flight. What follows in the thematic play is cross-checks with black correction. Absolutely gorgeous!

The first part is solved by 1.e3 f4 2.e2 f5 3.e1=R f6 4.Rg1 f7 5.Rg7 f8=S. When the white pawn is shifted to d4 in the twin, the solution changes to 1.e3 d5 2.e2 d6 3.e1=B d7 4.Bc3 d8=Q 5.Bcg7 Qd3. The Allumwandlung theme is economically shown in a white minimal setting. Both mates are models.

Andy Sag: This twin displays a complete set of promotions. In each case the promoted black piece completes the set of self-blocks and the promoted white piece mates without regal assistance.
Jacob Hoover: In both sequences Black's promoted piece self-blocks on g7 in order to allow White's to mate. Since all possible promotions are seen in the solution, this is indeed an Allumwandlung.
Nigel Nettheim: Easy to solve, thank heavens, but the point is the elegance of the pair. The promotions cover the full range: Q, R, B, S.
George Meldrum: Promotions to four different pieces. A very enjoyable problem to start the year off.
Ian Shanahan: The evergreen Allumwandlung theme in miniature with a white pawn Excelsior in part (a) and (obvious) smothered mates thrown in to boot. I have shown this theme in a helpmate-in-2 twin with a mere five units. Solving was not difficult. It's a pity that Black's first move is repeated and most of the black force remains static. In (a), the dual avoidance by the black rook promotee in reaching g7 is attractive. The wrong route fails because of ineluctable obstruction by the white pawn.