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326. David Shire
Australian Chess 2007
Mate in 2

The key 1.Rg4! protects e4 to create the threat, 2.Sb4. The variations 1…Re5 2.Sf6 and 1…Bc6 2.Sc7 show excellent, analogous play. In each case Black shuts off a white piece – the h8-bishop or the c8-rook – so that the threat-move, which interferes with the white queen, would give a flight on the fourth rank; but each defence also self-blocks, enabling a knight mating move that disrupts a line controlled by the same white piece cut off by Black. In 1…Rxh8 2.Rg5 and 1…Bxc8 2.Qxb5, Black removes the white line-pieces altogether but exposes the king to orthogonal mates on the fifth rank. 1…Sc2 2.Qxb3 and 1…Sd3 2.Qd4 see the black knight interfering with the queen on d1 twice to permit queen mates. The problem hence presents three pairs of corresponding variations. There’s by-play with 1…Ba3 2.Sxc3, 1…Rxe4 2.Qxe4, and 1…Qd4 2.Qxd4.

Andy Sag: The key guards the e4-knight threatening 2.Sb4 and leaves the queen en prise but frees it up to mate in four variations.
Jacob Hoover: In the diagram, the white queen – the only piece guarding the e4-knight – is threatened with capture by the b5-pawn. Of the squares near the black king that the white queen guards, all of them, with the sole exception of e4, are guarded by other white units. So the solution seems to be to put another guard on e4, and doing so also threatens 2.Sb4.

 
327. Frederick Hawes
British Chess Problem Society Tourney 1943
1st Prize
Mate in 3

The black knight has four legal moves including two checks, all with set play prepared: 1…Sb6+ 2.Qxb6 and 3.Qb1/Qb2/Qc5/Qc7; 1…Sc5+ 2.Qxc5; 1…Sb2 2.Qc5+ Sc4 3.Qxc4; and 1…Sc3 2.Qc5 and 3.Qa3/Qxc3. The key 1.Qg4! entails a short threat, 2.Qd1, and completely changes White’s answers to these defences. 1…Sb6+ 2.Kd6 (threat: 3.Qd1) Sc8+ 3.Qxc8, or 2…Sc4+ 3.Qxc4. 1…Sc5+ 2.Kc8 and 3.Qd1/Qc4. 1…Sb2 2.Qe2 and 3.Rc2. After 1…Sc3, not 2.Qc4? Qxg7! but 2.Qb4 (threats: 3.Qa3/Qb2/Qxc3) Sa4/Sd1 3.Qb1. In response to the knight checks, White makes a leisurely king move and, in the case of the first variation, invites two further checks!

Andy Sag: The threat is a short mate but we have all four possible knight moves providing a defence; the first variation involving successive checks is the highlight.
Jacob Hoover: After 1..Sb6+ and 1…Sc5+, if White moves the king anywhere other than the noted squares Black has a delaying check.

 
328. Edgar Bettmann
Henry Wald Bettmann &
Jacob Bettman

South Australian Chronicle 1883
Mate in 2

Set mates have been arranged for every possible black move: 1…d3 2.Qxd3, 1…e4 2.Qd6, 1…Ke4 2.Qf3/Qg2, 1…B~ 2.Bxb7, and 1…S~ 2.Sxf6. But White has no way of preserving all of these variations, e.g. 1.Qh2? d3!, 1.Qh3? e4! The withdrawal key 1.Qe1! (waiting) yields three new mates: 1…d3 2.e4 (nice en passant avoidance), 1…e4 2.Qxa5, and 1…Ke4 2.Qh1. The remaining play is unchanged: 1…B~ 2.Bxb7 and 1…S~ 2.Sxf6. The only flaw of this well-keyed mutate is the set dual, 1…Ke4 2.Qf3/Qg2, fixable by adding a white pawn on h2 and a black one on h3.

Andy Sag: Looks like an old classic; complete block with five variations including three changed mates.
George Meldrum: The range of tries, and the changed mates, combined with the innocuous looking key move make this a pleasing problem.

 
329. Arnoldo Ellerman
The Brisbane Courier 1919
1st Prize
Mate in 2

After the key 1.Qb2!, White threatens 2.Qg7/Qh8. Black has three defences on c3 that interfere with the b3-rook and unpin the white bishop on the third rank. This bishop is thus allowed to fire the R + B battery, playing to a different square each time to shut off a black line-piece. 1…Sc3 2.Be1, 1…c3 2.Bf4, and 1…Bc3 2.Be5. The direct unpin 1…Rxb2 enables the battery to fire one more time – 2.Bf2. A fourth defence on c3 sees the black rook closing one white queen line and opening another: 1…Rc3 2.Qb8. Lastly, 1…Rxg3+ permits 2.Rxg3.

Andy Sag: Sacrificial key and six variations, four involving different placements of the unpinned battery trigger bishop.
Jacob Hoover: A nice presentation of a line-effect theme. We also see a "defences on same square" thing going on.
Nigel Nettheim: Nice handling of the four defences on c3.
George Meldrum: An alluring setting with a wicked key move that provides threats by the double. But it is all in the variations, most of which centre around blocking the queen’s path on c3. My favourite is 1…Rc3 2.Qb8.

 
330. Niharendu Sikdar
Australian Chess 2006
Helpmate in 7

This tough helpmate is solved by 1.d5 a3 2.d4 axb4 3.d3 b5 4.dxe2 b6 5.e1(B) bxa7 6.e2 a8(Q) 7.e3 Qf3. Both thematic pawns depart from their initial ranks and eventually promote, so the Excelsior idea is doubled. The unusual motive for the black promotion accounts for the difficulty. Black promotes not for the purpose of employing the new piece (e.g. to self-block), but solely to clear e2 for the e3-pawn. A bishop promotion is required since another piece on e1 would either check White or control the mating square f3.

Andy Sag: Not hard to see that the promoted queen could get to f3 in seven moves but only if the e4-pawn was not there. Working out how to deal with the e4-pawn took forever. A number of near misses in eight moves make this a very difficult and tantalizing problem.
George Meldrum: I can personally vouch that there are about 20 other ways to do this in eight moves. It took most of my Saturday, and it was only in the freshness of Sunday morning when it came into view. There is only one was to describe this problem: frustratingly good.

 
331. Alexander Goldstein
Lunds Dagblad 1946
5th Hon. Mention
Mate in 2

The key 1.Se4! threatens 2.Sd6. The two black knights defend by capturing the white queen, to create a flight on e7. But each knight move also opens a white line to an eighth-rank square controlled by the e7-pawn, enabling White to promote on that square and give a pin-mate: 1…Sfxe6 2.exf8(Q) and 1…Scxe6 2.exd8(Q). The knight defences are thus anticipatory self-pins, and there’s a paradoxical element as well in that the white mates on f8 and d8 occur only after they have been guarded by the black knights. Two more thematic defences yield a flight by capturing the e7-pawn, and again they lead to pin-mates: 1…Qxe7 2.Qg8 and 1…Bxe7 2.Qc8. The impressive pinning strategy shown on the e-file also entails an exchange of functions between the white queen and pawn. One by-play variation is 1…Rc6 2.Qd7.

Andy Sag: All five defences have set mates including two pairs of pin-mates. The knight defences open white lines aimed at the promotion mating squares.
Nigel Nettheim: The capturing promotions make a nice symmetrical matrix, causing any black knight that ventures onto e6 to be pinned. The c3-rook and d3-pawn are not needed, but provide the minor variation; I’d vote to remove them.

 
332. Brian Tomson
The Problemist 1983
Series-helpmate in 17

A plausible mating scheme involves placing the black king on a8 and two pieces on a7 and b8 to self-block, and this would enable the white bishop to mate by capturing an interposing piece on the long diagonal. The self-blocking pieces must be bishops to avoid interfering with the mate, so Black promotes both pawns to this type of unit. And since to check during the move sequence is forbidden, Black uses the knights to shield the white king from the promoted bishops. 1.Sf6 2.Se4 3.Sf2 4.g1(B) 5.Bh2 6.Se4 7.Sd2 8.c1(B) 9.Ba3 10.Sb3 11.Sd4 12.Bc5 13.Ba7 14.Sb6 15.Sc6 16.Ka8 17.Bhb8 Bxc6.

Andy Sag: The final scenario with the black king on a8 is fairly obvious but how to get there in 17 moves without checks is the task.
Nigel Nettheim: The series of tasks in logic is elegant, though not difficult. For instance, a knight must occupy b6, for on c5 or d4 it would prevent mate.
George Meldrum: Another try was to get the black king to f1 and mate with Be2 but it just fails the 17 moves stipulation. The problem would have been much easier if the white king were on another square!
Andrew Buchanan: Not complicated but it was fun to follow the false trails and eventually see all the constraints that led to a unique story solution. Fun to see the knight and bishops dancing round the white king.

 
333. Joseph Opdenoordt &
Petrus Koetsheid

The Brisbane Courier 1930
5th Prize
Mate in 2

The initial position is a complete block, with set mates prepared for all of Black’s moves: 1…B~ 2.Qb2 and 1…g4 2.Qh4. The key 1.Qh2! (waiting) preserves the set play but also unpins the black knight. A random move by the piece opens a white queen line for 1…S~ 2.Qe5. Two correction moves disable the queen mate but they cause self-blocks that are exploited by the rooks: 1…Sg6 2.Rgf7 and 1…Se6 2.Ref7. A third correction interferes with the black bishop and permits yet another queen mate: 1…Sd3 2.Qh6.

Andy Sag: The key unpins the black knight to add four variations to the two already set in an economical eleven-piece setting.
Ian Shanahan: Three excellent corrections by the black knight.
George Meldrum: Quite a cute problem that frees the black knight to add to the set play with four new mates.
Nigel Nettheim: The black knight comes into play with 1…S~ 2.Qe5 and three nice corrections. Very economical.
Andrew Buchanan: 1.Ka2? gets checked and 1.Kb2? amusingly occupies a key square that White would need. 1.Qg3? (threat: 2.Qxg5) was promising but 1…Bg6! controls f7. Still the idea of pinning the black knight along a new line looks cool, and 1.Qh2! covers e5 indirectly. It's an obvious idea to have lots of black knight defences, to break the woodenness of the white symmetry. Perfectly dual-free.
Brian Stephenson: Clean, elegant setting with the c7-pawn being needed to stop the dual 2.Qd6 after some black knight moves. Much enjoyed.
Jacob Hoover: This problem had a lot of things for me to like: black correction, line effects, a complete block, and a proliferation of queen mates.

 
334. Abdelaziz Onkoud
Australian Chess Problem Magazine 1996
Mate in 3

The thematic set play consists of two pairs of variations that involve reversals of White’s second and third moves (as the A-B-C-D labels indicate): 1…Rxe4+ 2.fxe4+ [A] Bxe4 3.g8(Q) [B], 1…Bxe4 2. g8(Q)+ [B] Rxg8 3.fxe4 [A], 1…Rxd4 2.Sc7+ [C] Bxc7 3.Qxd4 [D], and 1…Bxd4+ 2.Qxd4+ [D] Rxd4 3.Sc7 [C]. After the key 1.Kd3!, Black’s four initial captures in the above variations all stop the threat of 2.Se3, but thanks to the white king’s new position, the continuations are all changed: 1…Rxe4 2.g8(Q)+ [B] Bxg8 3.fxe4 [A], 1…Bxe4+ 2.fxe4+ [A] Rxe4 3.g8(Q) [B], 1…Rxd4+ 2.Qxd4+ [D] Bxd4 3.Sc7 [C], and 1…Bxd4 2.Sc7+ [C] Rxc7 3.Qxd4 [D]. Again we see two reversals of White’s second and third moves. And further, an elaborate form of reciprocal change is rendered with respect to the set play, in that after each pair of defences, White swap not only the two second moves around but the two mating moves as well. There’s by-play with 1…Rc3+ 2.Sxc3+ Sxc3 3.Qb3. A dense pattern yet crisply shown.

Andy Sag: Short threat swaps bishop and rook checks and adds four changed mating plays to one preserved set play.
Brian Stephenson: The short threat of 2.Se3 just had to be investigated, which meant only one possible candidate for key, which I tried and so very quickly solved this. It was only after I finished writing down the variations that I realised that there might be a double reciprocal change. And there was!
Nigel Nettheim: A thematic key. The respective black rooks and bishops cannot both continue to guard the vital squares g8 and c7. A heroic doubling (or quadrupling) of the theme: alternated white second and third moves respond to alternated black bishop and rook captures. The d7-pawn avoids a dual 1…Rxe4 2.Bxc4+ Kc6 3.d5.
Jacob Hoover: A whole lot of reciprocal changes occur between the set and actual play, and the black rooks and bishops interchange roles. A very interesting theme here; and I enjoyed it immensely.
George Meldrum: A heavily engineered setting with full military precision. The battlefield contains diligent distraction tactics. A medal should go to General Onkoud.

 
335. Laszlo Apro
The Australasian Chess Review 1932
1st Prize
Mate in 2

The key 1.Qh3! threatens a pin-mate, 2.Qe6. Any black move to b4 or c4 would unpin the d4-knight and thwart the threat, and four such defences result in two pairs of mutual interferences between the rooks and bishops. 1…Bb4 2.Rc4, 1…Rb4 2.Sxc5, 1…Bc4 2.Sc3, and 1…Rc4 2.Qd3. Hence the problem exhibits a double Grimshaw, which is additionally unified by the common unpinning motive. Four other variations make up the by-play: 1…Qh2/Qh1 2.Sf2, 1…Bxe2 2.Rxe2, 1…e5 2.Sd6, and 1…f5 2.Qf3.

Brian Stephenson: With 1…Qxd1! taking a flight at e3 and unprovided, one is encouraged to look for a threat on the e-file to cover e3. That's going to be by the queen, so 1.Qh3! (2.Qe6) is soon found.
Andy Sag: The key sets up a pin-mate threat with four unpin defences including two already set, all creating interferences to allow different mates. Removal of the e2-pawn is answered by a required double-check mate and finally there are three set plays involving two unguards and a self-block making eight variations in total.
Nigel Nettheim: The main play is the pair of rook-bishop (Grimshaw) interferences on b4 and c4.
Jacob Hoover: Four moves unpin the knight and these occur in two Grimshaw pairs.
George Meldrum: Not much in new play after the key, but the problem forces you to work through some very nice variations. My choice one is 1…Bb4 2.Rc4.