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301. Molham Hassan
Australasian Chess 2013
Mate in 2

In this complete block position, every black move has been prepared with a white mating response. Only the key 1.Re2! (waiting) manages to keep all of these set variations in place. The d7-bishop illustrates focal play as it cannot maintain its guard of both b5 and f5: 1…Be6/Bc8 2.Sxb5 and 1…Bc6/Be8 2.Sxf5. A random move by the g4-knight, 1…S4~, permits 2.Bf6, while the correction 1…Se5 is a self-block that enables 2.Be3. White exploits a line-opening for the g6-bishop in 1…f4 2.c3. And the d2-knight mates twice with 1…S1~ 2.Sf3 and 1…a3 2.Sb3. Good tries include 1.Bf7? (waiting) f4!, 1.Bh7? (waiting) Be8+!, 1.Bxf5? (threat: 2.c3) Be8+!, and 1.Bd8? (threat: 2.Bb6) Se2!

Jacob Hoover: White preserves all of the set mates with 1.Re2!
George Meldrum: Could be quite baffling to someone who did not notice the set play.

302. Gerhard Latzel
The Australasian Chess Review 1934
6th Prize
Mate in 2

White utilises the half-battery on the f-file in the try 1.Be7? (threats: 2.Be4/Bg4/Be6), refuted by 1…Rf6! The key is made by the other white bishop, 1.Bg6!, which threatens 2.Bxh5. In two highly thematic variations, the black rooks leave each other pinned by the white queen and interfere with a3-bishop, enabling White to fire the R + B battery while shutting off each defending rook: 1…Rb4 2.Bd4 and 1…Rc5 2.Be5. Two more rook defences disable the a6-bishop and permit White to open the R + P battery: 1…Rb5 2.d4 and 1…Rc4 2.dxc4. There’s by-play with 1…Bxd3 2.Rxd3.

Andy Sag: Rook defences self-pin the remaining rook and block a black bishop line allowing either a vertical or horizontal rook battery mate, depending on which bishop line is closed.
Jacob Hoover: Another chess problem featuring battery play, with interferences and a half-pin as well! Yay!

303. Geoff Foster
The Problemist 2015
Ded. to Barry Barnes
Helpmate in 3½
2 solutions

This miniature is solved by 1…Kd5 2.Sf4+ Kc5 3.Re6 Sd6+ 4.Ke5 Sd7 and 1…Se6 2.Se5 Kc5 3.Rf6 Kd5 4.Sg6 Se3. In both solutions White must lose a tempo, and the king does so by visiting c5 and d5 in reverse order. Two ideal-mates complete a lovely problem.

Andy Sag: In each case the white king moves twice to lose a tempo.

304. Comins Mansfield
The Australian Meredith Tourney 1928
1st Prize
Mate in 2

If White unpins the d5-bishop then 2.Bf7 is threatened, but 1.Kc2/Ke2? fails to 1…Rxa8! while 1.Qd4? is defeated by 1…Kd7! The key 1.Qe2! threatens 2.Qxe7, which is still effective if Black takes the granted flight, 1…Kd7. The black knight defends by opening a line for the a3-bishop, and a random move 1…S~ allows 2.Qb5 (a change from the set mate, 2.Qa4). Two correction moves prevent the secondary threat 2.Qb5, but unpin the white bishop: 1…Sd3 2.Bc6 and 1…Sd7 2.Bf7. One more variation is 1…e6/e5 2.Rxd8.

Andy Sag: Meredith with queen withdrawal key giving a flight albeit non-defensive.
Jacob Hoover: The correction moves unpin the d5-bishop and allow it to mate.
George Meldrum: Effective and a flight square too.
Nigel Nettheim: The threat is not subtle, but everything else is really elegant, including some changed mates.

305. John James O’Keefe
Die Schwalbe 1932
1st Prize
Mate in 4

Several queen moves off the third rank, such as 1.Qf4?, threaten 2.Rxb3+ axb3 3.Qd6 (etc.) and 4.Qa6, or 2…Kxb3 3.Qe3+ (etc.) Kxc4 4.Qd3. But 1…Sg5! refutes because of the impending check on f3 or h3. The fine key 1.Qh6! doesn’t entail a threat, and the rook sacrifice is playable only after the black knight has weakened its position: 1…Sxf6 2.Rxb3+ axb3 3.Qxf6 Ka4 4.Qa6, or 2…Kxb3 3.Qe3+/Qh3+ Kc4 4.Qd3; 1…Sf8 2.Rxb3+ axb3 3.Qxf8 Ka4 4.Qa8, or 2...Kxb3 3.Qe3+/Qh3+ Kc4 4.Qd3. The star variation, however, is 1…Sg5 2.Bxg5 f6 3.Bc1 bxc1(Q)+ 4.Qxc1 (pin-model mate). Now we see that the key is a clearance move that allows the bishop to travel along the line traversed by the queen but in the opposite direction (a Turton manoeuvre), and this is capped off by a mating move in which the queen reverses its direction and follows the bishop on the same line.

Jacob Hoover: 1.Be7? threatening 2.Qc3 is a good try, refuted by 1…Sg5! This one was difficult to solve.
Andy Sag: The key is a line clearance allowing the bishop to work on the c1-h6 diagonal as well as keeping open the possibility of an a-file mate. The theme is stalemate avoidance. 3.Bc1 is a classic masterstroke.

306. Efren Petite
Australian Chess Problem Magazine 1995
Mate in 2

The thematic try 1.Qf2? (waiting) sets up a Q + S battery that fires directly after the king moves: 1…Kb6 2.Sec4 and 1…Kd4 2.Sexf5; but there’s no mate after 1…dxe6! The key 1.Qe7! (waiting) creates another Q + S battery, and it works indirectly after the flights: 1…Kb6 2.Sdc4 and 1…Kd4 Sdxf5. Two unusual changed mates in which different knights play to the same squares. If 1…dxe6 then 2.Qxa7.

Andy Sag: Key preserves all three set legal moves including the two flights and sets up an indirect battery to guard c5. Easy to solve.
Nigel Nettheim: The try uses the e3-knight; the key uses the d6-knight moving to the same squares.
Jacob Hoover: 1…dxe6 2.Qxa7 is a pin-mate. This one's easy once you realize that the only white unit that isn't participating is the queen.
Paz Einat: Pales in comparison to earlier works. The price of two unprovided flights and a white queen out of play is just too high.

307. Michael McDowell
Tony Lewis &
John Nunn

Australian Chess Problem Magazine 1993
Helpmate in 2
2 solutions

The solutions are 1.Bxc6 dxc8(Q) 2.Kd5 Qf5 and 1.Qxd7 Qxb7 2.Ke6 Qe4. The two parts show reciprocal captures between the white queen and the b7-bishop, and between the white pawn and the black queen. The Zilahi theme is also seen in that the two white units swap their roles in giving mate and getting captured. The echo mates are brought about by rather symmetrical play, though the pawn promotion in one solution helps to break the symmetry.

Andy Sag: In each case the black capture prepares a self-block so the (original or promoted) queen can mate after the king moves to its final position.
Jacob Hoover: In each solution Black's first move is a necessary self-block (in the 1.Qxd7 solution this move is also an unpin), and Black's second move puts the king in a position where it is the least mobile.
Nigel Nettheim: A white queen functions similarly in both mating positions. Without the g7-bishop there would also be 1.Ke6 dxc8(S) 2.f5 Qxd6, but Black’s move order is not forced.

308. Linden Lyons
Australasian Chess 2010
Mate in 2

All black moves in the diagram are provided with set mates, and 1.Kh7! (waiting) is the only way to maintain the block. The two black knights illustrate correction play: 1…Sd~ 2.Sf6, 1…Sdxe3 2.Qa8, 1…Sf~ 2.Sg3, and 1…Sfxe3 2.Qg6. In each case, random moves by the knight permit its white counterpart to mate, while the correction capture on e3 – removing a guard of f4 – self-pins the piece and enables a queen mate. These four black knight variations are supplemented by four involving black pawn defences: 1…exf4 2.Qxe6, 1…f2 2.Qg2, 1…dxe3 2.c3, and 1…d3 2.cxd3.

Andy Sag: The key invites a royal fork (1…Sf6+) but leaves all eight set mates undisturbed and also eliminates a dual after 1…Sfxe3 (2.Qh7).
Nigel Nettheim: Black is stymied; the key is the only available waiting move and it eliminates the dual after 1...Sfxe3. Very neat.
George Meldrum: Not 1.Qxe6? f2!, or 1.Qg7?/Qg5?/Qg4? exf4! Tried every queen move on the board, then realized had picked the wrong royal. Frustratingly simple.
Jacob Hoover: Two knight corrections and two pawn moves allow mates from four diagonal directions.

309. Denis Saunders
The Problemist 1990
Mate in 3

The key 1.Qc2! contains a quiet threat, 2.Ke3 and 3.Qxg6, and if 2…exd4+ 3.Sxd4, 2…exf4+ 2.Sxf4, and 2…e4 3.Qxe4. Black has three defences on b5, of which two are more strategic because they involve self-obstructions on that square. After 1…Sxb5 (which thwarts the threat because of 2.Ke3? exd4+!), White can play 2.Kf3 since …cxb5+ is disabled, and the threat of 3.Qxg6 provokes 2…Sxd4+ 3.Sxd4 and 2…e4+ 3.Qxe4. And 1…Rxb5 (to answer 2.Ke3? with 2…Rb3+!) precludes …Sxb5 or …cxb5+, enabling White to continue with the square-vacating 2.dxe5 and 3.Sd4. The third defence on b5 is a discovered check that unguards d5: 1…cxb5+ 2.d5+ Bxd5+ 3.cxd5. If 1…Rbf8/Rgf8 then 2.exf8(S)+ Rxf8 3.Re7. There are some short variations: 1…exd4 2.Sxd4, 1…exf4 2.Sxf4, and 1…g5 2.f5. Including the threat play, the white king invites multiple checks while standing on e4, e3, and f3.

Jacob Hoover: Note that in 1…Sxb5 2.Kf3 Sxd4+ 3.Sxd4, with the king off the e-file the e5-pawn is pinned! The all-checks variation 1…cxb5+ 2.d5+ Bxd5+ 3.cxd5 is a nice touch.
Andy Sag: Cross-check theme with heaps of variations from the Wizard of Oz. A few shorts as well but what the heck!

310. Molham Hassan
Australasian Chess 2011
Version by Andy Sag
Mate in 2

The sacrificial key 1.Se6! (threat: 2.Sxc5) vacates the diagonal controlled by the black B + S battery, setting off the cross-check 1…Sd~+ 2.d6. The white B + P battery fires again with 1…fxe6 2.dxe6. Various black queen defences unguard d3 or e3 and the white queen mates accordingly: 1…Qxc4/Qe3 2.Qe3 and 1…Qxg4/Qf2/Qd3 2.Qd3. And the c4-knight mates twice with 1…Qxd2 2.Sxd2 and 1…Bg1 2.Sxd6. Hence there are three pairs of variations, each employing the same mating piece.

Andy Sag: Sacrificial key allows a check. Threat plus six variations comprising pairs of pawn moves to discover mate, queen mates and knight mates. Tries: 1.Sa6? (2.Sxc5) Qxd2!, 1.Rxe2+? Bxe2 2.Qe3, but 1…Kd4!
Jacob Hoover: This one was made easy due to the fact that only one white unit (the c7-knight) wasn't participating.
Nigel Nettheim: The key was not hard to find, despite the f7-pawn, because the latent cross-check was bound to be used. Several variations, no duals. The c5-pawn prevents an extra threat, 2.Rd4.

311. Christopher Jones &
Ian Shanahan

Australian Chess 2004
Helpmate in 3
2 solutions

The first solution 1.Sd4 Ra5 2.Rb5 cxd4 3.Rb6 d5 begins with a knight sacrificing itself to activate the white pawn. The white rook makes a clearance move to allow its black counterpart to follow along the same line – this illustrates an idea called the Loshinsky’s magnet. The black rook is thus able to self-block on b6, and the pawn mates with the support of the white rook. In the analogous second solution, 1.Sb4 Bb8 2.Bc7 cxb4 3.Bb6 b5, the black knight is sacrificed to the same pawn but on another square. The white and black bishop pair executes a diagonal version of the Loshinsky’s magnet, aimed at giving the black piece access to b6 for a self-block. Lastly the white pawn mates on a different square, supported by the rook from another direction. A fine example of an orthogonal-diagonal transformation. The only flaw is that while the white rook’s move shows a nice anti-critical effect by crossing over the eventual mating square d5 (so avoiding a self-interference in the mate), the white bishop’s move doesn’t have a similar effect.

Andy Sag: Perfect twin in typical Jones style. In (1) the black rook self-blocks on b6 and the white pawn mates on d5. In (2) the black bishop self-blocks on b6 and the white pawn mates on b5. The three black pawns are there to stop cooks; some are very subtle, e.g. if a black pawn is not on f2, then 1.e5 Rxe5 2.Kc7+ Kg1 3.Kc8 Re8.

312. Joseph Nidiry
Chess World 1947
Mate in 2

A white king move off the diagonal would threaten 2.Bd2, but most attempts fail to black checks: 1.Ka3? a1(Q)+!, 1.Kb3? a1(S)+!, 1.Kc5? Rc8+!, and 1.Kc4? Rc8+/Bf7+! Only 1.Kb5! works, and this fine key still elicits three checks. 1…Be8+ interferes with the f8-rook and permits the cross-check 2.d7, while 1…Rf5+ cuts off the g6-bishop and leads to another cross-check, 2.d5. So Black’s rook and bishop close lines controlled by each other, but unlike an ordinary Grimshaw, the mutual interferences here take place on different squares. The third check is answered by a more straightforward recapture, 1…Bxd3+ 2.Sxd3, which in turn is similar to 1…Rxe2 2.Sxe2. The h4-knight has two defences; one cuts off the g6-bishop again but the weakness is exploited differently: 1…Sf5 2.Re4, and the other is a self-block: 1…Sf3 2.e3.

Nigel Nettheim: The key walks into three checks, but the a4-rook and a5-bishop had to be activated. Six interesting variations.
Andy Sag: The highlight of this problem is the first pair of checking defences where the resultant black interferences allow cross-check mates. A pair of pawn capture defences allow knight mates. A pair of knight defences make up a total of six variations.
Jacob Hoover: The mutual interferences and cross-checks in this problem make it a lovely one.

313. William Lester
The Brisbane Courier 1923
2nd Prize
Mate in 2

Every black move in the diagram has been provided with a set mate: 1…Sd~ 2.Rxe4, 1…Sa~ 2.Qxc5, 1…Sb6 2.Qa1, 1…b6/b5 2.Qg7, and 1…exd3/exf3 2.Bxe3. Tries that aim to maintain the block include 1.Kb1? Sc3+!, 1.Se1? Sc3!, and 1.Sb2? Sb6! The latter try-move disables 2.Qa1 mate and it goes well with 1.Re7? which prevents 2.Qg7 mate after 1…b6/b5!, though the pair of refutations means the rook move isn’t technically a try. The key 1.Se5! (waiting) generates plenty of changes. 1…Sd~ 2.Rc4, 1…Sa~ 2.Qxc5, 1…Sb6 2.Qa1, 1…Sc3 (a new correction) 2.Rd2, 1…b6/b5 2.Sc6, and 1…exf3 2.Sxf3. Splendid mutate. The white bishop, used as a mating piece in the set play, is required to pin the e3-pawn in a post-key variation.

Jacob Hoover: The key causes an almost complete change in the play.
Andy Sag: Near try 1.Re7? b6/b5! Complete block with four changed mates. The 1…Sc3 self-block allows a pin mate.
Nigel Nettheim: Most mates are changed (though not 1…Sb2 2.Qxc5 and 1…Sb6 2.Qa1). 1…Sb6 2.Qa1 nicely recalls 1…b7~ 2.Qg7. 1…Sc3 2.Rd2 is excellent.

314. György Bakcsi
Chess in Australia 1979
1st Commendation
Helpmate in 2
Set play

In the set play, 1…Ra4 2.Kxa4 Sd4, the white rook sacrifices itself to allow the black king to reach a4, where it’s mated by White firing the B + S battery. When Black commences, there’s no waiting move that could preserve the set play, and the solution becomes 1.Kxc4 Bd5+ 2.Kxd5 Sd6. After an initial capture, it’s the white bishop that sacrifices itself to give the black king access to d5; then White mates with the R + S battery aimed at that square. The rook and bishop swap their roles in getting captured and giving mate, so the Zilahi theme is produced. The b5-knight nicely opens both batteries which operate on different lines.

Nigel Nettheim: The theme is white sacrifice. The b5-knight fires a different battery in each phase. The back piece of the battery and the sacrificed piece exchange roles in the two phases. The mate is model and the set mate nearly so.
Jacob Hoover: There is a definite battery-play theme here, but there is also a diagonal-to-orthogonal transformation effect where the bishop and rook interchange roles between the set play and actual play.

315. William Whyatt
problem 1957
1st Prize
Mate in 2

The black king has two unprovided flights on e4 and e5, and the key 1.Sg2! threatens a queen mate that covers these squares – 2.Qe3. Now both king defences, 1…Ke4 and 1…Kxe5, are answered by 2.Qf4, though because the king is mated on different squares, these variations may be regarded as distinct. Black has three more defences on e4, committing self-block errors that are exploited in a variety of ways: 1…Be4 2.f4, 1…Sce4 2.Rxd5, and 1…Sge4 2.Sf3. Likewise, there are three further defences on e5 that prevent the king from escaping to that square: 1…Bxe5 2.f3, 1…Qxe5 2.Rxb4, and 1…Rxe5 2.Qc4. Eight thematic variations!

Nigel Nettheim: Four defensive captures on e5 and four defensive moves to e4, with some wonderful mates. Virtuoso playing by two quartets. A nice open and materially balanced position.
Andy Sag: Try 1.S3g4? Ke4! The key leaves the e5-knight en prise and Black can defend by either capturing it or by blocking on e4.
Jacob Hoover: 1…Qxe5 2.Rxb4 sees a removal of a dual from the set 1…Qxe5 2.Rxb4/Qc4, and 1…Bxe5 2.f3 shows a change from the set 1…Bxe5 2.Qc4. Eight defences and eight distinct mates. Nice.

316. Herbert Ahues
Australian Chess Problem Magazine 1996
Mate in 2

Any move by the white knight on d3 would guard that square and threaten 2.c3. A random try by the knight, 1.Sd~? (e.g. 1.Sc1?), fails to provide for 1…Bg6!, pinning the white pawn. Further tries by the knight correct this error by exploiting the interference of the h6-rook caused by the bishop move. Thus 1.Sxf4? Bg6 2.Se6, but now 1…Rg3! refutes because the knight has obstructed 2.Qxf4. Similarly, 1.Sdxc5? Bg6 2.Se6, but there’s no answer to 1…Ba5! as the knight has prevented 2.Qxc5. One more correction try is 1.Se5?, which leads to the changed mate 1…Bg6 2.Sc6, and it’s defeated by 1…Qh7! when 2.Be5 is ruled out. Finally, the key 1.Sb4! works by avoiding the self-obstructions. 1…Bg6 2.Sc6, 1…Rg3 2.Qxf4, and 1…Qh7 2.Be5. It’s a pity that 1…Ba5 no longer stops the threat, though the missing variation is compensated by 1…cxb4 2.Qxb4. A clear illustration of white correction play.

Nigel Nettheim: Good. Well-controlled tries.
Jacob Hoover: Sacrificial key.
Andy Sag: Two pin defences allow minor piece mates. Remaining two defences allow lateral queen mates.

317. Vladimir Alexandrov
Australian Chess Problem Magazine 1992
Helpmate in 2
3 solutions

This miniature is solved by 1.Sf3 Qf2 2.Se5 Bf5, 1.Kd3 Qc1 2.Be4 Bc4, and 1.Bc4 Qg5 2.Bd3 Bd5. The same mating configuration occurs in all three solutions but on different parts of the board, so a triple echo is shown. The first two mating positions display a reflection echo, while the first and the third exemplify the rotation type.

Jacob Hoover: In each solution the black knight and bishop take up self-blocking positions so that the queen and bishop can deliver a model mate in the centre of the board. Another thing the three solutions have in common is that the three mates are echoes of each other.
Andy Sag: The king on a7 stops the knight from going via c6 in the first solution.
Nigel Nettheim: Of the nine squares, the white queen will cover five: three black, the mating bishop and another white one. The white bishop will cover two, and the black pieces the remaining two. It seems surprising that there are three dual-free ways to do this.

318. William James Smith
The Brisbane Courier 1914-15
1st Commendation
Mate in 2

The diagram is a complete block position in which white mates are prepared against all legal black moves. 1…Kd4 2.Qd2, 1…Sg~ 2.Se2, 1…Sd~ 2.Be5; most bishop moves permit a dual by opening the fourth rank – 1…B~ 2.Bb4/Rc4, though 1…Bc2/Bd3/Bd5 are answered uniquely by 2.Bb4. White is unable to maintain the block with a waiting move, e.g. 1.Kh6? Sf5+, 1.Rf4? h4! The surprising key 1.Bf4! not only closes the fourth rank but carries a threat, 2.Qd2. Three changed mates result: 1…Kd4 2.Qc4, 1…Bc2 2.Qa1, and 1…Bd3 2.Bd2 (the latter reactivating the white rook). One more variation in this deceptive block-threat problem is 1…Sf1 2.Se2.

Andy Sag: Pin-mate in the set variation, 1…Kd4 2.Qd2.
Nigel Nettheim: The set knight-play is reduced after the key, when only 1...Sf1 2.Se2 is needed.
Jacob Hoover: A very nice threat-mutate.

319. Laimons Mangalis
The Problemist 1966
Mate in 3

After the key 1.Qc1!, White threatens 2.Qxe3 followed by 3.Qh3, and if 2…fxe3 3.Sxe3, or 2…f3 3.Qg5. Black has three pawn defences, in each case partially opening a line that remains blocked by another black pawn. White responds by sacrificing a unit to the second pawn, in order to open the line fully. 1…d2 2.f3 (threat: 3.Rh5) exf3 3.Qb1. 1…cxd4 2.Rxd5+ cxd5 3.Qc8, or 2…Be5 3.Rxe5. And 1…e2 (to answer the threat 2.Qe3 with 2…exf1(Q)) 2.Sg3+ fxg3 3.Qg5. The line-openings are all utilised by the white queen in the three harmonious variations.

Andy Sag: Threat and three variations sacrifice a piece on the second move. Three diagonal, long-range queen mates and one short mate. Position is legal involving eight captures of white pieces/pawns.
Jacob Hoover: A masterfully crafted three-mover featuring strategic play.

320. Robert Lincoln
Australian Chess 2003
Mate in 2

The key 1.Bb8! creates three threats, all rook mates: 2.Rc5/Rd6/Re5. Black’s play allows these mates to occur in every possible combination. Only one black move does not disable any threat – 1…Bg7 2.Rc5/Rd6/Re5. Three defences allow different dual mates by preventing one of the threats: 1…Se6 2.Rd6/Re5, 1…c3 2.Rc5/Re5, and 1…Bxf6 2.Rc5/Rd6. Another three defences force each of the rook mates individually: 1…Sf7 2.Rc5, 1…d3 2.Rd6, and 1…Sb7 2.Re5. Lastly, one move eliminates all of the threats but provokes a new mate, 1…Sxc6 2.Be6. This unusual theme, in which dual mates appear by design, is known as total combinative separation.

Nigel Nettheim: The pattern of black moves and white mates, including duals, is evidently considered to be the point of interest. Eccentric.

321. Chris Feather
Australian Chess Problem Magazine 1994
Helpmate in 3
Twin (b) Pf3 to f2

The diagram part is solved by 1.cxd5 Ba7 2.Kf4 Bb8 3.Qg4 Sxd5. The initial capture of the bishop on d5 is aimed at giving the white knight access to that square in the eventual mate. White sets up a B + S battery with the remaining bishop, while Black positions the king and finishes with a self-block by the queen. Part (b) is solved by 1.Rxe3 Bxc6 2.Kg2 Sd5 3.Sg3 Sxe3. Now it’s the bishop on e3 that gets captured but for a similar purpose – to clear that square for the knight’s mating move. The other white bishop is employed to form a B + S battery, which fires after a black king move and a self-block by the e4-knight. The two solutions vary in interesting ways – e.g. their move orders are forced using different techniques – but overall there’s great unity in the battery play rendered along two diagonal lines.

Andy Sag: Twin double-checks from batteries set up on move 2. Had a tough time until I realised that in each case one white bishop must be removed to allow the white knight to end up on that square. Note that the g6-pawn is a cook-stopper in (a) involving the knight mating on f5, and the d2-pawn is a cook-stopper in (b) involving the rook self-blocking on f1.
Nigel Nettheim: A celebration of the power of the double-check. The white knight had to be brought into play, which assisted solving, and the d2-pawn is needed for (b) only. But each first move is a surprising capture, and the perfect twinning seems amazing.

322. Johannes Rietveld
The Brisbane Courier 1914-15
2nd Prize
Mate in 2

The key 1.e6!, which threatens 2.Qf4, thematically opens the fifth rank and enables the f5-bishop to give a number of discovered checks. Indeed Black has no defence other than to check with this bishop, and four variations result. 1…Bxe6+/Bxd3+ – an unguard and a self-pin respectively – 2.Qe5. 1…Bxg4+ is also an unguard and by creating a flight on f3, it induces the cross-check, 2.Sc5. 1…Be4+ is a self-block that leads to another cross-check, 2.Sf5. And 1…Bg6+ interferes with the g7-rook and permits 2.Bxg5. A black bishop-star is produced, an idea not commonly seen in directmates.

Nigel Nettheim: The latent cross-checks suggest the key, after which the play is clever with a mixture of (self-)pins and batteries. The h7-pawn prevents 1…Bh7, and the c6-pawn prevents 1.Sxf5+ Ke4 2.Qc6.
Andy Sag: Key allows discovered checks all answered by cross-checks as the f5-bishop provides line interference, self-block, self-pin, etc. The white pawn on c6 can be omitted if the black pawn is shifted from f7 to d7.
Jacob Hoover: A nice black correction theme with cross-checks thrown in for good measure. An old problem, but a good one.
Thomas Thannheiser: The threat 2.Qf4 also works on 1...Bxg3 because the bishop is pinned. Nice cross-check problem.

323. H. Beechey
Australian Columns Tourney 1917
2nd Prize
Mate in 2

Two self-blocking pawn moves produce important set play: 1…e5 2.Sc5 and 1…cxd5 2.Re6. The key 1.Qh5! controls e5 and threatens 2.Sc5. Paradoxically 1…e5, which initially enables 2.Sc5, now defends against it (by cutting the queen’s line to d5), and a changed mate results: 2.S7f6. Another change occurs with 1…cxd5 2.Qg4. The original answer to 1…cxd5 is transferred to another defence: 1…c5 2.Re6. Such a combination of changed and transferred mates (with respect to the 1…cxd5 defence) creates a Rukhlis pattern, though the proper Rukhlis theme requires the idea to be doubled. Black commits two more self-blocks with 1…Bf5 2.Qh1 and 1…Sd3 2.Bg2. Lastly, 1…Sa4 allows 2.Rxa4. Whether the Dombrovskis-type paradox and the Rukhlis effect shown were intended or not, this century-old problem seems ahead of its time!

Nigel Nettheim: A wonderful collection of tries, so not easy to solve. 1…Bf5 2.Qh1 is very nice.
Andy Sag: Hard to solve until you realise that the key frees up the d7-knight whereas in set position the d5-knight is free to move. Three defences are diagonal self-blocks.
Jacob Hoover: Very nice.

324. Charles G. M. Watson
The Leader 1918
Australian Columns Tourney 1918-19
1st Prize
Mate in 2

The waiting key 1.Re2! completes the block. Each of the two black pawns has the maximum possible four legal moves, and they all generate different white responses. 1…c6 2.Sc7, 1…c5 2.Qc6, 1…cxb6 2.Sxb6, and 1…cxd6 2.Qxd6 involve two interferences with the black rook and two square-clearances. 1…f6 2.Se7, 1…f5 2.Re5, 1…fxe6 2.Bxe6, and 1…fxg6 2.Rxg5 show two interferences with the black queen, one square-clearance, and one unguard. The Pickaninny theme is therefore brought about twice. The by-play consists of simple unguards by three black pieces. 1…S~ 2.Qd4. The black rook is preventing three mates on the c-file, two of which are forced by 1…Rc6 2.Qxc6 and 1…Rc5 2.Qxc5; duals follow 1…Rc4 2.bxc4/dxc4 and 1…R-else 2.Sxc7/Qc6/Qc5. The black queen is also stopping three mates, with two separated by 1…Qf6 2.Bg2 and 1…Qf5/Qh5 2.Se7; other queen moves allow various combinations of 2.Bg2/Se7/Re5, except for 1…Qxf4 2.Se7/Sxf4. The try 1.Re1? is defeated by 1…Qf6!

Andy Sag: Waiter with countless variations. The main point appears to be the eight variations involving all possible moves of the two pawns and these are dual-free, and arguably one – 1…fxg6 2.Rxg5 – is a changed mate (different rook).
Jacob Hoover: The main theme seems to be the Pickaninny shown with the black pawns, with the black corrections being almost an afterthought in my opinion.
Nigel Nettheim: Quite elaborate, but spoiled by the duals – one in the set play and many (including three triples) in the actual play.

325. Janos Csak
Australian Chess Problem Magazine 1997
Helpmate in 2
Twin (b) BBf3

If the two white bishops were allowed to cover the knights standing next to the black king, the queen would be freed to mate on the seventh rank. But three black pieces are in the way, two of which if moved could check the white king by discovery. Dealing with these hurdles, the white queen captures one of the three black pieces (self-pinning itself) on its way to the seventh rank, while the other two black pieces open the white bishop lines and, simultaneously, close black lines to avoid checking White and to unpin the white queen. 1.Rg3 Qxe4 2.Sg4 Qh7. Part (b) has a black bishop starting on f3, and it’s solved by 1.Bg4 Qxf2 2.Sg3 Qf7. Two perfectly matched solutions with terrific line-play.

George Meldrum: The twin position gave away the key move somewhat. Clearing the lines for the two white bishops seemed to baffle me for quite some time. Neatly done.
Andy Sag: An accurate twin comprising a tale of two batteries: the f3-piece deactivates one battery, the queen self-pins by capturing a knight, and the remaining knight unpins the queen which then mates.
Jacob Hoover: This wasn't too difficult for a helpmate.