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 201. Herbert Grant The Australasian Chess Review 1930 Mate in 3

Since 1.Ra2? stalemates, White waits for the black bishop to move before checking on the a-file. Only the key 1.Rc2! (waiting) manages to cope with every bishop defence, retaining all of the set play: 1…B~ 2.Ra2+ Ba5 3.Rxa5, 1…Bb6 2.Ra2+ Ba7 3.Rxa7, and 1…Bb4 2.Ra2+ Ba3 3.Rxa3. Not 1.Rb1? Bc3!, 1.Rb3? Bb4!, 1.Rb7? Bb6!, or 1.Re2? Bd2! Another good try is 1.Bc7? leading to 1…Ka7 2.Ra2 Ka6 3.Rxa5 (ideal mate), but 1…Bb6! 2.Ra2+ Ba7. The actual play is simple but only five pieces are used and there are plenty of tries.

Nigel Nettheim: This problem reminds us that a three-mover is not necessarily harder to solve than a two-mover, and might even be a lot easier. Following No.200, the relief was welcome, rather like being given an “early mark” at school.
Dennis Hale: Not an easy problem to solve.

 202. Matthew Fox The Australian Problemist 1962 1st Hon. Mention Mate in 2

The key 1.Sd2! threatens 2.Qxe4. When the black queen moves, it brings about a remarkable number of dual-free variations. Two groups of ‘random’ moves lose control of e5 or the d6-d4 line: 1…Qe5/Qc6/Qb7/Qa8/Qg6 2.Qe5 and 1…Qxd3/Qe3/Qe2 2.Qd6. The correction 1…Qd5 self-blocks, allowing 2.Qe3. Other correction moves are answered by the queen’s capture, and in three cases this involves opening the R + B battery: 1…Qxe6 2.Bxe6, 1…Qxf3+ 2.Bxf3, 1…Qf5 2.Bxf5, 1…Qxg4+ 2.Rxg4, and 1…Qf4 2.Rxf4. Also, 1…Re7/Sc5 2.Qc4.

Nigel Nettheim: The two candidates (1.Sd2 and 1.Sd6) have an unsubtle threat (2.Qxe4), but the point is the choice between them. That turns out to depend upon Black’s 1...Qxd3, which I found difficult to spot. As far as I can see, the a4-pawn should be removed. The a6-knight is also extraneous, but it provides a fairly good variation 1...Sc5 2.Qc4. Such a piece may be tolerated or not according to personal preference, and here I find it quite OK.

 203. Ernest Jerrard The Brisbane Courier 1918 3rd Prize Mate in 2

The diagram is a complete block position, with every black move set with a mating reply: 1…exf2 2.e3, 1…Sb~ 2.Ra4, 1…Sc4 2.Rd3, 1…Sc~ 2.Se6 and 1…g3 2.Sf3. White cannot maintain the block with a simple waiting move, e.g. 1.Raa3? Sc4! Instead the key is 1.Rc2! (waiting) which generates two changes: 1…exf2 2.Bxf2 and 1…Sc4 2.Bc3. The other variations are as set: 1…Sb~ 2.Ra4, 1…Sc~ 2.Se6, and 1…g3 2.Sf3. A fine mutate in which the position after the key would also work as a sound two-mover, solved by reversing the key-move, 1.Rc3!

Nigel Nettheim: The two changed mates (for 1...Sc4 and 1...exf2) are excellent.
Ian Shanahan: The problem seems cumbersome, but closer scrutiny shows it to be as economical as possible. I saw immediately that it was a complete block – indeed, a mutate – which proved difficult to solve. Bravo!

 204. Rurik Bergmann Chess in Australia 1980 Mate in 3

The Novotny try 1.Sg5+? cuts off both the g6-rook and h6-bishop, provoking 1…Bxg5 2.Sxg3 and 1…Rxg5 2.Sd2 (or 2.Re3), but 1…Qxg5! is adequate. The key 1.Ba1!, threatening 2.Re5, lures the black queen to a defensive position where it becomes overloaded: 1…Qf6 2.Sg5+ Qxg5 3.Re5, while the Novotny play is retained without the dual: 2…Bxg5 3.Sg3 and 2…Rxg5 2.Sd2 (1…Qh8 2.Sg5+ is similar). If 1…Bf4, the bishop also becomes overloaded: 2.Sd2+ Bxd2 3.Re5. 1…Be3 obtains a flight-square on d3, but results in a dual mate: 2.Re5+ Kd3 3.Rexf3/Rfxe3. (And 1…Bg7 2.Sd2.)

Nigel Nettheim:It is a little unfortunate that the b4-pawn and a3-pawn serve only to rule out 1.Bc3 and 1.Bb2, so they point towards the key. An alternative would be to replace the a3-pawn with a white b2-pawn. Then the key would be 1.Bc3! and the variation 1...bxc3 2.Re5+ Kd4 3.bxc3 would be added. (The d7-pawn could be removed too, adding a short variation 1...Qxd6 2.Sxd6 which, however, the composer might not have fancied).

 205. Bertram George Fegan The Brisbane Courier 1913 Mate in 2

After the key 1.Qd7! (threat: 2.Qxd4), Black defends by closing the white queen’s line to d4. These defences on d5 and d6 by Black’s rooks and bishops result in two pairs of Grimshaw interferences: 1…Bd5 2.Sc5, 1…Rd5 2.f4, 1…Bd6 2.c5, and 1…Rd6 2.Sf4. Here the four white mating moves are also quite harmonious – two battery mates are delivered by the pawns, which play to the same squares used by the pair of mating knights. However, that these thematic mates also follow other black defences is a little distracting: 1…Be5 2.Sc5 and 1…Bb6/Rf4 2.c5. There's by-play with 1…Sc3 2.Sb2.

Nigel Nettheim: The theme is mutual interference (“Grimshaw”) between the black rooks and bishops. The variation 1...Rf4 2.c5, with interference by the white pawn, is nice too. If the a2-knight were removed, the variation 1...Sc3 2.Sb2 would be lost, but the position would become a little cleaner, with less distraction from the theme; its removal might be a matter of personal preference.

 206. Laurie Hill Chess in Australia 1977 Mate in 2

The give-and-take key 1.Se6! (waiting) offers two new flights to the black king but removes an existing one on f4. Moving to the flight on e4 allows an attractive model mate: 1…Ke4 2.Qxh7, while accepting the sacrificed knight on the other flight yields 1…Kxe6 2.Qf7. The other variations show straightforward unguards, but they are unified by the “close-encounter” queen mates: 1…B~ 2.Qg6, 1…S~ 2.Qg4, and 1…d5 2.Qe5.

Nigel Nettheim: The strong defence 1…Kf4 must be provided for, and the only way is to prevent it. But the try 1.Sh3? allows 1…Ke4! when there is no mate because 2.Qxh7 leaves d4 unguarded. The sacrifice 1.Se6! guards that square so that 1…Ke4 2.Qxh7 is now mate, and that is the standout variation. It is nice that 1…e6 and 1…e5 were provided with 2.Qf6, yet with the key White gives up that resource.

 207. A. E. Ramsey Chess World 1946 1st Hon. Mention Mate in 2

The flight-giving key 1.Qb4! unguards the e4-knight but controls d2, threatening 2.Sc5. If the black king takes the flight – giving a discovered check – White answers with a battery mate: 1…Kxe4+ 2.Sxf3. More battery play follows with 1…Qd1+ 2.Sc2, 1…Qf7+ 2.Se6 (two cross-checks), and 1…Qf5 2.Sxf5; in these variations White exploits the pin of the g3-bishop after the black queen has moved. The half-pin on the third rank is made complete by 1…Bxd6 2.Sf2, when a bishop move leaves the black queen pinned and unable to prevent the mate. Lastly, the self-block 1…Qxe4 permits 2.Qc3.

Nigel Nettheim: The key offers a sacrifice that gives check (1…Kxe4+ 2.Sxf3). The h4-pawn prevents the cook 1.Rxg3.

 208. Alexander Goldstein Warsaw Kurier 1931 Mate in 4

The thematic try 1.Bg4? prepares for 1…Kb5 2.Bf3 Ka5 3.Be2 followed by 4.Ra6 mate, but Black is stalemated on the third move! The actual play sees White arranging a similar mating net, but with an additional plan to provide Black with a spare move: 1.Bh3! Kb5 2.Bxg2 Ka5 3.Bf1 g2 4.Ra6. So by removing a black pawn, the white bishop releases another one and stalemate is averted. A pointed idea shown in miniature form.

 209. Gordon Stuart Green Time & Tide 1952 Mate in 2

Set play is provided for every black move in the diagram: 1…S~ 2.Qxe4/Sd3, 1…Se3 2.Sd3/fxe3, 1…Sxd6 2.Sd3, 1…Sb2/Se5 2.Qxe4, 1...e3 2.fxe3, 1…g3 2.fxg3/hxg3, and 1…B~ 2.Rf5. Unusually, such a complete block position is solved by a key that entails a threat: 1.Qc6! (2.Qxe4), making this an example of a block-threat. The queen has abandoned the half-pin on the fourth rank, effecting two changed mates: 1…Sxd6 2.Qxd6 and 1…e3 2.Sd3 (also a mate transference), while a set dual is removed: 1…Se3 2.fxe3. Taking the sacrificed queen produces another new mate: 1…dxc6 2.Sxe6. Lastly, 1…Bd5/Bf5 still allows 2.Rf5.

 210. John Lindsay Beale Check! 1945 Mate in 2

The key 1.Sd5! (waiting) is delightful in granting three flights to the black king. Since the king has access to all four diagonal flights now and each brings about a different mate, the star-flights theme is shown: 1…Kc6 2.Sa7 (model mate), 1…Kxa6 2.Sc7 (sideboard model), 1…Ka4 2.Sc3 (pure mate but not a model because the white pieces on e4 and c8 are not involved), and 1…Kc4 2.Sxd6.

Nigel Nettheim: Two clues make this easy to solve. (a) The b2-pawn can be of use only if the black king moves towards it, so the key piece must be the b6-knight. (b) The strong defence 1...Kxa6 requires 2.Sc7. Thus 1.Sd5! Then follows the “star” theme, in which the black king may move to each of the four corners of its field.

 211. Molham Hassan “Berlin Wall” OzProblems.com 6 Dec. 2014 Mate in 2

The occupied diagonal represents the Berlin Wall, and when the black pieces move they evoke the Wall’s falling stones. The long-range key is 1.Bh6!, a waiting move. The h8-knight facilitates two nice bishop mates: 1…Sf7 2.gxf7 and 1…Sxg6 2.Bxg6. The other black units are forced to either unguard a square – 1…Sg~ 2.Qe6 and 1…d3 2.Se3 – or open a line for White – 1…e4 2.Qd5, 1…c2 2.Rf3, and 1…b1(Q) 2.Qf2.

Composer: The key-piece moves from the beginning of a diagonal to its end, in a straight line parallel to the Wall. The knights on g7 and h8 stand for the horses of the Berlin Quadriga, which was built on top of the Brandenburg Gate in 1793. Later they became a symbol of German national identity.
Nigel Nettheim: No mate is set for 1…d3 or 1…bxc1(Q), and both those black moves require the c1-bishop to move to an appropriate square. The a1-bishop is not needed for the problem, but it is needed to complete the Berlin Wall, and attractive pictorial effects are one of Molham’s specialties, as is seen in his autobiography on this site.

 212. Ian Shanahan The Problemist Supplement 2005 Mate in 6

The try 1.Bf8? crosses over the critical square e7 to prepare for a self-interference, 2.Ke7, followed by 2…Kc5 3.Ke6 mate, but Black is stalemated by the try. To set up a similar mate without allowing such an escape, White executes a pericritical manoeuvre in which the bishop goes around the critical square instead of passing over it. 1.Bf4! Kc5 2.Bd2 (attacking b4 to keep the black king trapped on c5 and d5) Kd5 3.Bh6 Kc5. Now 4.Bf8+ brings the bishop to its target square, but unlike the try 1.Bf8?, the move is timed correctly to avoid stalemate, forcing 4…Kd5 5.Ke7 Kc5 6.Ke6. A splendid miniature.

Composer: There is also a thematic (intentional) pericritical try: 1.Bc7? Kc5 2.Ba5 Kd5 3.Bd8 Kc5 4.Be7+ Kd5 5.?? The white bishop obstructs the white king on the critical square!

 213. William James Smith Sydney Daily Telegraph 1901 Mate in 2

The square-vacating key 1.Bb3! threatens 2.Qd5. When Black defends with the d7-bishop and its adjacent pawns, they cut off one another’s line of action: 1…Bc6 2.Qa7, 1…c6 2.Qa4, 1…Be6 2.Qh8, and 1…e6 2.Rxg4. Hence the problem demonstrates two Pawn-Grimshaws – pairs of mutual self-interferences by a bishop and a pawn. Two secondary variations are 1…c2 2.Qa1 and 1…Rg5 2.Qe4. The key-bishop must be placed carefully, e.g. not 1.Ba2? c2! or 1.Bf7/Bg8? Be6!

Nigel Nettheim: The d5-bishop must vacate its square while keeping c4 guarded, and the key is the only way to do this without disadvantage. Black’s occupations of c6 and e6 provide the main (symmetrical) variations, the bishop and pawns mutually interfering, thus showing two “Grimshaws”.
Imanol Zurutuza: A very nice problem: Pickabish theme doubled!

 214. John James O’Keefe Club Argentino de Ajedrez 1920 Version 3rd Hon. Mention Mate in 2

All possible black moves have been given set mates, including 1…B~ 2.Qe6/Bd7 – a dual separated by 1…Be6 2.Qxe6 and 1…Bd7 2.Bxd7 – as well as 1…Sh~ 2.Rf4. A fine key 1.Qd3! (waiting) exposes the white king to a check while creating a Q + R battery. The black bishop variations are changed to 1…B~ 2.Bd7 (dual removed) and 1…Be6+ 2.Rc4. Another change is 1…Sh~ 2.Qf3, with the correction move 1…Sf4 forcing 2.Re5. The black rook also shows correction play: 1…R~ 2.Sh6 and 1…Rxg4 2.hxg4. Two more variations, 1…Sd~ 2.Se3 and 1…c5 2.Qd5, round off a good mutate.

Nigel Nettheim: The two rather symmetrical cases of loss of control of a square in a set mate (1…Be6 2.Qxe6 and 1…Sf4 2.Rxf4) being changed to self-blocking of that square in the changed mate (2.Rc4 and 2.Re5) are a very nice feature. The construction seems excellent.
Geoff Foster: A very nice problem, with two new battery mates, including a surprising cross-check.

 215. Stephen Bicknell Australian Chess Problem Magazine 1993 Mate in 2

The out-of-play position of the white queen makes the key easier to find: 1.Qc3! (waiting). Now the queen delivers seven mates, all in response to black unguards: 1…b4 2.Qc4, 1…c4 2.Qd4, 1…g3 2.Qf3, 1…h3 2.Qg3, 1…Bd2 2.Qxd2, 1…Be3 2.Qxe3, and 1…Rf6/Re5 2.Qe5. The black rook sets off three other variations: 1…Rg5 2.Bxg5, 1…Rxh5 2.Sxh5, and 1…Rxd5 2.Sxd5. Lastly, 1…Sg8 2.Rxf5 and 1…f6 2.Se6.

Nigel Nettheim: The b6-knight has to take part, which can only be by 1…Rxd5 2.Sxd5, so White must guard e5. Hence 1.Qc3! which also provides for 1…b4/c4/g3/h3, as well as for 1…Re5/Rf6 and 1…Be3. The key is perhaps not the main feature, but the play of the queen against the two pairs of black pawns shows neat symmetry.
Andy Sag: I enjoyed solving Stephen's problem, a waiter with twelve variations including seven queen mates. Why not add a white rook on a1 and make it thirteen, including eight queen mates!? (1…bxa1(Q) 2.Qxc1.)

 216. Brian Tomson Chessics 1984 Series-helpmate in 19

By promoting the three pawns and using the new pieces to self-block, Black is able to arrange various mating configurations, e.g. c8K, b7S, c7R and d7B for Ra8 mate, or h4K, g3S, g4R and g5R for Rh2 mate. These matrices take more than the required 19 moves to set up, however, and the solution sees Black using two promoted pieces to self-block and the third to interpose on the a-file, allowing the king to be mated on a8. 1.h5 2.h4 3.h3 4.h2 5.h1(S) 6.Sg3 7.Sxf5 8.Sd6 9.f5 10.f4 11.f3 12.f2 13.f1(B) 14.g1(R) 15.Rg8 16.Ba6 17.Ka8 18.Sb7 19.Rb8 for Rxa6. If the h6-pawn were to start on h7, there would be a cook: 1-6.Kh2 7.Kg1 8.Kf1 9.g1(R) 10.Rg2 11.Kg1 12.Kh2 13-18.Kg8 19.Rg7 for Ra8.

Nigel Nettheim: The attempt with g1(S) and h1(R) takes one move too long, because the knight’s path is then not minimal. Instead, h1(S) gives the knight its most direct path, via the pawn placed on f5 for that purpose. The elegance of this problem impressed me very much when it first appeared, and induced me to try my hand at composing a few similar ones.
Andy Sag: Nice one involving three different sub-promotions and avoidance of checking or moving into check to ensure only one possible solution.

 217. Thomas Denton Clarke The Australasian 1885 Version Mate in 2

A good withdrawal key, 1.Qa1! (waiting) completes the block. The black queen cannot maintain its focus on two corner squares: 1…Q~rank 2.Qh1 and 1…Q~file 2.Qa8. The g7-knight permits the same queen mates after the self-interferences, 1…Sh5 2.Qh1 and 1…Se8 2.Qa8, while its only other move self-blocks: 1…Sxe6 2.Bc6. Correction play is shown by the black bishop; the random 1…B~ allows 2.Qe5 – a queen mate disabled by three specific bishop moves, which yield 1…Bc7 2.Sxc7, 1…Bxf4 2.Sxf4, and 1…Bb8 2.Qa8. The white queen does more work with 1…Sf~ 2.Qd4 and 1…c3 2.Qa2. Lastly, 1…exd2 2.e4. The e7-pawn has been added to the original position, to prevent the unfortunate duals that follow 1…Be7 and 1…Bf8.

Nigel Nettheim: The key 1.Qa1! is thematic, for the main interest lies in the queens facing off from opposite corners. It suggests the title “She Stoops To Conquer”.

 218. Juan Kloostra & Denis Saunders The Problemist Supplement 1999 Mate in 3

The aggressive key 1.Qc5! is fairly obvious, as White must deal with the two unprovided flights on b2 and c2. However, it’s surprising that no threat is generated by the key. That means Black’s seemingly nondescript pawn moves actually entail specific weaknesses that White will exploit. 1…c6/cxd6 unguards b6: 2.Qxd4+ Kxb4 3.Qb6, or 2…Kc2 3.Qd1. 1…a5 is a distant self-block: 2.Qxd4+ Kxb4 3.c5, or 2…Kc2 3.Qd1. When Black takes the flights, it’s a pity that White answers with the same queen move we have already seen: 1…Kc2 2.Qxd4 (threat: 3.Qd1) Sc3/Sd2 3.Qc3, and 1…Kb2 2.Qxd4+ Sc3 3.Qxc3, or 2…Kc2/Kc1 3.Qd1. A good castling variation completes the play: 1…Sd2 2.0-0-0 (3.Bxd4) Sf3 3.Sxe4, or 2…Sxb3+ 3.Rxb3.

 219. William J. McArthur The Brisbane Courier 1913 5th Commendation Mate in 2

The splendid key 1.Rf1! yields a flight on g6 and abandons the prominent set variation, 1…Sg5+ 2.Rxg5. The threat is 2.Qb1. Now 1…Kg6+ is answered by the cross-check 2.f5 – also a pin-mate. The set play is changed to 1…Sg5+ 2.fxg5, and 1…Se5 2.fxe5 sees the R + P battery firing again. The c8-knight provides the by-play with 1…Sxd6 2.Sxd6 and 1…Sf6 2.Se7. The white queen is a little underused, though it controls g5 and h6 in the flight-taking variation.

Nigel Nettheim: The fine key allows the impressive cross-check variation; at the same time, it changes the mate after 1...Sg5+. The a5-bishop efficiently counters 1.Bxf7? (2.Rg5/Bxe6) with 1…Bd2! and 1.Rxg8? (2.Se7) with 1…Bd8/Bd2! The low award in the 1913 competition may be explained by the strong international field.

 220. Srbo Zaric Australian Chess Problem Magazine 1993 Mate in 2

After the key 1.Bg4!, White threatens 2.Qf5. Black commits two self-block errors with 1…Qd5 2.Qxf4 and 1…Sd4 2.Sf2. A couple of self-interferences occurs in 1…Be6 2.Qe5 and 1…Sd6 2.Sc5. Finally, Black unguards twice with 1…Rxg5/Rf6 2.Sf6 and 1…Re5 2.Qxe5, though the latter variation repeats the queen mate seen after 1…Be6. A cleanly constructed position with no white pawns; however, its economy could be improved: shift the g8-knight to h7, and replace the b4-knight and the g6-rook with black pawns on b4 and g7 (1…g6 2.Sf6).

Brian Stephenson: 1...Rxg5, giving a flight, is not set with a mate and it appears clear that 2.Sf6 is the intended mate after that, so the key, guarding f5 to provide just that mate, is soon found. There are two self-blocks (one with white interference), two black interferences and two unguards. Not richly thematic, but very pleasant.

 221. Nigel Nettheim The Problemist 1984 Series-selfmate in 13

To force Black to mate, a promising plan is to place the white king on a1 for a deflection finish, Bb2+ Bxb2 mate. The scheme requires White to promote to a queen for controlling the black king’s flights on c2, d2, and d1 from d3 (not e2 as the queen would stop the mate), but this takes too long, e.g. 1.e4 2.e5 3.e6 4.Kxb3 5.Ka2 6.Ka1 7.e7 8.e8(Q) 9.Qe4 10.b4 11.Bc3 12.d4 13.Qd3 14.Bb2+ Bxb2. In the solution, the white king surprisingly goes to c3 instead, though again the aim is to play Bb2+ (from a1) Bxb2 mate. Now White must guard the king’s flights on b1 and d1, and the quickest way involves a nice underpromotion. 1.e4 2.e5 3.e6 4.Kxb3 5.Kc4 6.b4 7.Ba1 8.Kc3 9.e7 10.e8(B) 11.Ba4 12.Bc2 13.Bb2+ Bxb2.

Andy Sag: First tried with king to a1, then c3 and I kept trying to get a promoted queen to d3 to cover b1 and d1 but not b2 or c1, but this could only be done in 14 moves. Then realised that a bishop on c2 would do the trick.

 222. Frederick Hawes & Frank Ravenscroft Weekly Times 1955 Mate in 2

The thematic key 1.Se6! (threat: 2.Qa8) unpins the e5-bishop and grants a flight on d5. The freed bishop defends by vacating e5, and it produces a remarkable number of dual-free variations. In 1…Bd4+/Bc3 2.Sed4, 1…Bf4 2.Sxf4, and 1…Bc7/Bb8 2.Sc7 the direct Q + S battery mates are assisted by the indirect B + S battery which opens to attack d5, while in 1…Bxg3 2.Sxg3 and 1…Bd6 2.Sxd6 it is the R + S indirect battery on the rank that is used to regain control of d5. White employs the B + S battery two more times, once directly if Black takes the flight – 1…Kd5 2.Sg5, and once indirectly with 1…Rxc5 2.Sxc5.

Nigel Nettheim: It seemed likely that 1…Bd4+ would be allowed, but the threat 2.Qa8 was well-hidden, and the e5-bishop moves are handled with very good variety. The b2-knight is needed to counter 1.Sb7, and the c2-rook could not be replaced by a black pawn because of the cook 1.Qe6.

 223. Henry Tate Brisbane Courier 1913 Mate in 2

The waiting key 1.Sg5! gives the black king an extra flight on e5. Now the three available moves of the king form a Y-pattern and they bring about different mates – 1…Ke5 2.Sf3, 1…Kc5 2.Se6, and 1…Kxd3 2.Se3 – so the Y-flights theme is displayed. The three mates are also all models. If the white rook were to start on d7 instead, a valuable try would be added: 1.Sd8? Kxd3! with a changed mate after 1…Ke5 2.Sc6.

Nigel Nettheim: This shows some of the powers of the knights in a nice and simple way.

 224. Alfred Figdor Chess World 1947 Mate in 2

The thematic try 1.Sd5? (threats: 2.Sxc3/Sc7) sacrifices the knight to three pieces and unpins the black queen: 1…Qxd5/Qb8+ 2.Qb8, 1…Bxd5 2.Rb6, and 1…Sxd5 2.c4. But 1…Sf5! (ensuring that the queen stays unpinned) refutes, since the try-piece on d5 has prevented 2.Bc6. The key 1.Sf5! (2.Sd6) again shows a triple sacrifice of the knight and frees the queen: 1…Qxf5/Qb8+ 2.Qb8, 1…Bxf5/Bd5 2.Rb6, and 1…Sxf5 2.Bc6. The c3-knight causes two self-interferences: 1…Sd5 2.c4 and 1…Se4 2.Sxd4. The latter variation makes clear the advantage of the key over a second try, 1.Sc8? Se4!

Nigel Nettheim: It seemed likely that the queen would be unpinned, after one had noticed 1…Qb8+ 2.Qxb8. The main choice is between 1.Sd5 and 1.Sf5, but 1.Sd5? Sf5! no longer allows 2.Bc6. The g7-pawn avoids letting 1…Qxg5+ make the key obvious. The unpinning key shows just a little similarity to No.222 Hawes & Ravenscroft.
Jacob Hoover: All set mates are preserved after the key, plus: 1…Qb8+ 2.Qxb8 and 1…Se4 2.Sxd4.

 225. John Angus Erskine The Leader 1916 Mate in 3 Twin (b) Shift all pieces one square north-east

The diagram position is solved by 1.Sd8! (waiting), with two variations: 1…Kb5 2.Kc3 Kc5 3.Ra5 (ideal mate) and 1…Kc5 2.Rb3 Kd5 3.Rb5. An equivalent solution is not possible in position (b), but now 1.Rb6! (waiting) works, followed by 1…Kc4 2.Sa7 Kc5 3.Rc6. Simple play but the twinning is clever and only five pieces are needed.

Nigel Nettheim: The twin removes one square (d8) from the reach of the b7-knight, compensating for that with another square (a7). Each part is nice, although no theme is apparent.