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226. James Joseph Glynn
The Adelaide Observer 1881
Mate in 2

The superb key 1.Sc5! (threat: 2.Sxe6) concedes two flights to the black king by cutting off the c7-queen and b5-rook. A battery mate follows one flight-move – 1…Kc3 2.Sxb3, but not the other – 1…Kxe5 2.Qg7. White’s first move is also an active sacrifice, which generates 1…dxc5 2.Qxc5. The black queen has two defences that allow the e3-rook to gain control of the c3-flight: 1…Qc4 2.Sc6 and 1…Qxb5 2.Qxd6.

Nigel Nettheim: The play is excellent, as well as the try 1.Rc5? (threats: 2.Qxd6/Sc6) Qa6! However, the a1-knight and b3-pawn can be removed, adding the variation 1...Qb3 2.Sxb3. Also, the b7-knight might better be placed on d7.

226b. James Joseph Glynn
The Adelaide Observer 1881
Version by Nigel Nettheim
Mate in 2

 
227. William Whyatt
The Tablet 1961
Mate in 2

In the set play, a random move of the d6-knight unguards b5 and opens the white queen’s line to c5, enabling 2.Sb5. The correction 1…Sxe4 allows 2.Qxe4. Moves of the e8-knight are answered by 2.Qxf6, though there’s a dual with 1…Sg7 2.Qxf6/Qxd6. White cannot preserve all of these variations with a simple waiting move, e.g. 1.Qf8? Sxe4!, and the key is 1.Qd8! (waiting). Now the d7-pawn becomes pinned after any d6-knight move: 1…Sd~ 2.S7e6. Another pin-mate follows the correction, 1…Sxe4 2.S5e6. Lastly, 1…Se~ permits 2.Qxf6 with no duals. The keys in mutates are typically perfunctory, but here the self-confining queen move is a delight.

Jacob Hoover: A complete block, in which the key changes the mates for the moves of the d6-knight. A very clever mutate that makes use of the half-pin tactic.
Nigel Nettheim: Among the many fine details, I appreciated the use of the top and left board-edges to limit the range of motion of several pieces.

 
228. Lajos Steiner
Magyar Sakkvilág 1935
Mate in 3

White must provide for 1…Kb8 when the king threatens to escape to the c-file, and the only way is 1.Rf1! (waiting). Now after 1…Kb8, which self-pins the e5-pawn, White has 2.Rc1 forcing 2…Ka8 3.Rc8. If 1…e4+, White avoids the stalemate-inducing 2.Kxe4? or 2.Ke3?, and instead plays 2.Kg2 to prepare for a battery mate, 2…e3 3.Kg1. The composer was an over-the-board IM who won the Australian Chess Championship four times in the 1940s and 1950s.

Jacob Hoover: A great key 1.Rf1! preserves the set continuation after 1…e4+ and meets 1…Kb8 with 2.Rc1, which keeps the king from moving further out.
Nigel Nettheim: It is nice that in the main variation, 1…e4+ 2.Kg2, all white moves are retreating. The h3-pawn forces the final retreat. Could this be called the “platypus” theme, after one of the shyest and most retiring of animals?

 
229. George Meldrum &
John Mazzieri

Chess in Australia 1983
Mate in 2

The directmate part of the solution is 1.exd6 e.p.! e5 2.Qa8. The en passant key is legal because we can prove by retro-analysis that Black’s last move could only have been …d7-d5. Black couldn’t have just played …Kg8-h8 since on g8 the king would have been in an impossible check from three white pieces. Black also couldn’t have made a pawn capture on d5 or e6 as the last move. This is because White is missing only the two bishops, and the black-squared one couldn’t have reached either of the two white capture squares, while the white-squared one was trapped on its home square f1 by the pawns on e2 and g2 and so couldn’t have been captured elsewhere. One other potential last move, …d6-d5, is ruled out because it would mean White was in check during Black’s turn. That leaves …d7-d5 as Black’s only possible last move.

This popular two-mover with a difference was solved by Nigel Nettheim, Andy Sag, Jacob Hoover, and Dennis Hale.

 
230. Laimons Mangalis
The Problemist 1979
Mate in 2

All possible black moves have been provided with set mates: 1…Re4 2.Sd8, 1…Qxg6 2.Rxg6, 1…f4 2.Rxe5, 1…Bc5 2.Sxc5, 1…Bd4 2.Sxd4, and 1…Ba5 2.Sc5/Sd4. White cannot maintain the block with any waiting move, however, e.g. 1.Rh6? Qxh6!, 1.Rh5? Qxg6!, 1.Rg1? f4!, or 1.Bg3? h2! The flight-giving key 1.Rxf5! entails a threat, 2.Rxe5. Two changed mates occur with 1…Re4 2.Qxd5 and 1…Qxg6 2.Bd7. Taking the flight gives 1…Kxf5 2.Qg4, while 1…Rxf5 is followed by a transferred mate, 2.Sd8. One more variation is the unchanged 1…Bd4 2.Sxd4. A great example of the less common block-threat type.

Nigel Nettheim: Everything seems excellent, including the key and especially the changed mate 1…Qxg6 2.Bd7.
Jacob Hoover: The surprising key grants a capture-flight on f5. An interesting block-threat with a very attractive pin-mate theme.

 
231. Ian Shanahan
OzProblems.com 2015
Is this checkmate position legal?
Twin (b) WRh7
(c) Ph3 to e5
(d) Ph3 to d6

(a) No. Black is mated by the bishop, but the piece couldn’t have just played to h1. The only way White could have given the check was by playing Pg2xh3; however, with a white pawn on g2, the white bishop could never have reached h1. That means White has no possible last move in the diagram and the position is illegal.
(b) Yes. White’s last move must have been Rb7xh7, capturing a black piece (not a pawn). This black piece had just played to h7, so Black was not at risk of having no possible last move. Therefore the position is legal.
(c) No. White’s only potential last move was Pe4-e5, but Black had no legal move prior to that. Black couldn’t have played Ka7-a8, because on a7 the king would have been in an impossible check from the b6-pawn and h7-queen.
(d) Yes. The last move wasn’t Pd5-d6 (for reasons similar to those in part (c)), but White could have mated with an en passant capture on d6! The following retraction sequence demonstrates how the position could have arisen: -1.Pe5xd6 e.p. Pd7-d5 2.Pe4-e5+ Ka7-a8 3.Pb5-b6+ (or Pxb6+). Note how once the uncaptured black pawn has retracted to d7, it shuts off the white queen, thereby allowing the black king to retract to a7, where the piece is in check from the white pawn only.

Composer: Rather off-beat – a black Rex Solus retro with multiple parts, in miniature.
George Meldrum: This lightweight setting gives an instant appeal and the first three tasks pass the eye with an enjoyable smile only to conceal the complexity that is yet to yield in the last task that is really a blast.
Nigel Nettheim: Clever twins.
Dennis Hale: Bravo to Ian! This is a fine retro twin incorporating a range of clever ideas.

 
232. J.T. Eaton
The Australasian Chess Review 1940
Version
Mate in 2

The highly thematic key 1.Sc3! not only unpins the black rook but also grants a flight on f6. The freed rook has four defences against the threat of 2.Qxg7, provoking two pairs of battery mates: 1…Rxd6 2.Sd5, 1…Rf4 2.Se4, 1…Ra4+ 2.Sxa4, and 1…Rd1+ 2.Sxd1. The flight-taking 1…Kf6 is answered by 2.Qe7. Most moves by the g5-knight defeat the threat but allow the same queen mate: 1…Se4/Sf7/Sh7 2.Qe7, while the correction 1…Se6 permits 2.Sd7.

George Meldrum: Whenever I see the name Eaton I expect something enjoyable. Nice key and the variations 1…Rxd6 2.Sd5 and 1…Rf4 2.Se4 are superb.
Nigel Nettheim: The key is good, though the immediate appeal of countering the rook checks made it easy to find. The g4-pawn is not needed; the h3-knight, which prevents some cooks, could be replaced by a black pawn on h6, producing a more natural and more economical position (1.Sxg5? hxg5! and 1.Sf2? h5!).

 
233. Arthur Charlick
Hampstead and Highgate Express 1907
3rd Prize
Mate in 2

White mates are prepared against most of Black’s moves, and the key 1.Sf1! (waiting) completes the block. The star variation, made possible by the sacrificial key, is 1…exf1(Q)+ 2.Rc2 – here the white queen exploits the opening of the e-file to control e5. A random move by the black rook produces 1…R~ 2.Qf2; the correction 1…Rg2 cuts off the black bishop and allows 2.Rf4. Since 1…Bg2 reciprocates the interference, enabling 2.Qf2, the Grimshaw theme is shown. The other bishop move is a square clearance: 1…Bxf3 2.Sxf3. The well-utilised queen gives four further mates: 1…h3 2.Qh4, 1…d2 2.Qxd2, 1…S~ 2.Qc3, and 1…a4 2.Qb4.

Jacob Hoover: A pair of Grimshaw interferences in 1…Rg2 2.Rf4 (this was the point of guarding e3 with another piece) and 1…Bg2 2.Qf2.
Nigel Nettheim: Wonderful. The provision for the h4-pawn with 1…h3 2.Qh4 is very pleasing; and 1…exf1(Q)+ 2.Rc2 is brilliant, e5 being newly protected. Evidently the composer died a few years after this was published, aged not quite 35.

 
234. Vassily Lapin
Chess World 1961
Mate in 2

The white queen takes a step back with 1.Qg8! to threaten 2.Qb8. Black’s d4-knight, the thematic piece, defends by opening a line for the rook on d3. In completing its move, however, the knight also closes various black lines of defence, and four such self-interferences are exploited by White: 1…Sb5 2.Sxc6, 1…Sc2 2.Sxd3, 1…Se2 2.Re4, and 1…Sf3 2.Qg3. A fifth move by the knight commits the error of self-block: 1…Sf5 2.Sf7. There’s one variation of by-play, 1…f5 2.Qxh8.

Jacob Hoover: Square-vacating key. A very classy (near) knight-wheel theme.
Nigel Nettheim: Five eighths of a knight-wheel. The h8-bishop prevents a dual after 1…f5; however, it could better be replaced by the white king.

 
235. Charles G. M. Watson
Melbourne Leader 1917
Mate in 5

The key 1.c5! guards d6 and traps the black king in the f4-e5 cage. There is a full-length threat: 2.Sb4 Ke5 3.Sxc6+ Kf4 4.Se7 Ke5 5.Sg6. But this is stopped by Black’s only legal move 1…Ke5, since now 2.Sb4? Kf4 3.Sxc6 is stalemate. White plays 2.0-0 instead, subtly motivated to allow the knight to attack from the king-side and to support the f2-pawn with the rook. 2…Kf4 3.Se1 Ke5 4.Sg2 fxg2 5.f4. Note that the try 1.0-0? could transpose to the solution after 1…Ke5 2.c5, but it’s refuted by 1…c5! Bob Meadley calls this problem “a classic” in his recent paper on the composer.

Nigel Nettheim: Excellent! An alternative setting is possible by reflecting the position along the e-file and then placing the rook on a1: 1.g5! Ke5 2.0-0-0. The a1-rook has more freedom than the h1-rook and 0-0-0 is a rarer move in chess games.
George Meldrum: Set up the chess set to solve this one… no need… hmmm… maybe I will need to after all. Nice!
Jacob Hoover: I usually don't like stalemate-avoidance problems, but this one had a delightful anticipation theme that I very much enjoyed. I also enjoyed the fact that one of the moves was a castling move and that the black king was mated by a bunch of pawns. Great job, Mr. Watson.

 
236. H. W. Fitzell
Chess World 1946
Version
Mate in 2

After 1.Rb5! White threatens 2.Bd5, which fires the Q + B battery while covering the e4-flight. Black’s queen and b8-bishop defend by pinning themselves on e5, anticipating that the threat move will unpin them and allow them to interpose on f6. However, White exploits these self-pins – called Schiffmann defences – with 1…Qxe5 2.Seg3 and 1…Bxe5 2.Sd6 (also 1…Bd6 2.Sxd6). If Black takes the flight, White utilises the Q + B pair again, but now as an indirect battery: 1…Kxe4 2.Bg6. Lastly, the self-block 1…Sxe4 enables 2.Qc8.

Jacob Hoover: The thematic defences are self-pins that allow pin-mates from the e4-knight.
Nigel Nettheim: Finding the key gave a real “light-bulb moment”. Not 1.Ra5/Rc5? Be8!

 
237. Joseph Heydon
Good Companions 1921
3rd Prize
Mate in 2

The diagram shows a complete block position, with every black move given a set mate: 1…Se~ 2.Sf3, 1…Sg~ 2.Se6, and 1…B~ 2.Bxc3. The set play cannot be retained with any simple waiting move, e.g. 1.Kg1? Be3+! The flight-giving key 1.Se3! (waiting) brings about an almost complete change of play: 1…Se~ 2.Sc2, 1…Sg~ 2.Sf5, 1…B~ 2.Qxc3. Now 1…Bxe3 is a correction move that disables the queen mate, but due to the self-block it allows 2.Bxc3 once more. An added mate results when the black king captures the offered knight: 1…Kxe3 2.Qe4. A well-constructed mutate that increases the number of variations from three in the set to five in the actual play.

Nigel Nettheim: A good key with a double sacrifice. The description “all change here” does not quite apply, because of 1…Bxe3 2.Bxc3.

 
238. L. H. Searle
Check! 1944
Version
Mate in 2

The black king has two diagonal flights, one of which is unprovided or without a set mate. The waiting key 1.Sxg4! completes the block, whereupon both flight-moves provoke pin-mates by the b5-knight: 1…Kf5 2.Sd4 and 1…Kd5 2.Sc7. The other black moves all permit queen mates, either by opening white lines – 1…R~ 2.Qf6, 1…f6/f5 2.Qd7, or by unguarding mating squares – 1…Sf~ 2.Qe5, 1…Sb7 2.Qxf7.

Nigel Nettheim: After 1.Se~ Kd5, 2.Sc7, but only 1.Sxg4! works. The black king’s other flight is also self-pinning, doubling the theme.
Jacob Hoover: Any move by a black unit other than the king allows the queen to mate at point-blank range.

This problem was originally cooked by 1.Sxf3; it's fixed by adding the g4-pawn but the latter results in a capture-key. Nigel Nettheim has found a better correction that avoids such an aggressive key – see the setting below (1.Sh3!) which uses a black bishop instead to stop the cook. Another advantage of this version is that 1.Se6? becomes a good try that’s defeated only by 1…g5!

238b. L. H. Searle
Check! 1944
Version
Mate in 2

 
239. Peter Wong
Phénix 1992
Shortest proof game in 12
2 solutions

In each solution, both white bishops are captured to facilitate Black’s promotion to a second white-squared bishop. The first game goes 1.a4 g5 2.Ra3 Bg7 3.Rb3 Bxb2 4.Rxb7 f6 5.Rb4 Ba6 6.Bxb2 Bxe2 7.Be5 Bd3 8.Bf4 gxf4 9.h4 f3 10.Rh3 fxg2 11.Rf3 gxf1B 12.Rff4 Bh3. The second part involves another precise sequence of play, one that brings about the thematic exchange of places for two pairs of pieces: 1.h4 g5 2.Rh3 Bg7 3.Rb3 Bxb2 4.Rxb7 f6 5.Rb4 Bb7 6.Bxb2 Bxg2 7.Be5 Bh3 8.Bf4 gxf4 9.a4 f3 10.Ra3 fxe2 11.Rf3 exf1B 12.Rff4 Bd3. So the identities of the two white rooks and the two black bishops in the diagram are swapped across the two phases.

Andy Sag: Had a bit of fun with this. I finally cracked it after realising that the black g-pawn can reach f1 via e2 instead of g2.

 
240. Ernest Jerrard
The Brisbane Courier 1918
Mate in 2

The key 1.Sc7! observes e6 to threaten 2.Qc5. The half-pin arrangement on the fifth rank is unusual in that the thematic black units – the f5-pawn and the g5-knight – are also the front pieces of batteries aimed at the white king. When either black unit defends by giving a discovered check, the other is left pinned, a weakness that White then exploits: 1…f4+ 2.exd3 and 1…Sg~+ 2.Sxg4. Three secondary variations are: 1…c3 2.Sxd3, 1…Be4/Rxg3 2.Qxd4, and 1…Sxc7/Sf6 2.Qf6.

Jacob Hoover: Beautiful. I enjoyed the 1…f4+ 2.exd3 line in particular, due to it involving a battery mate in response to a battery check.

 
241. Ian Shanahan &
Ray Proudfoot

Chess in Australia 1983
Mate in 3

Set play is arranged for the black king’s two possible moves: 1…Ke3 2.Sf4 Ke4 3.Re2 and 1…Kd5 2.Bg2. Despite the freedom of White’s overwhelming force, there’s no waiting move that could retain both set variations. The surprising key 1.Rc1! (waiting) changes the continuation after 1…Ke3 to 2.Sf2, followed by the sub-variations 2…Kxf2 3.Bd4 and 2…Kd2 3.Bf4. The short mate 1…Kd5 2.Bg2 is unchanged. A three-move mutate that’s tougher to solve than it looks!

Jacob Hoover: Eureka! 2…Kxf2 3.Bd4 is a model mate.

 
242. Arthur Mosely
Good Companions 1914
Mate in 2

The key 1.Sg5! threatens 2.Se4, against which Black has three unified defences on the same square. These moves to g3 unpin the e5-rook and enable White to fire the Q + R battery. In each case, the black move has an additional effect that compels the white rook to land on a particular square on the e-file. 1…g3 opens the fourth rank: 2.Re4; 1…Rg3 controls the third rank: 2.Re3, and 1…Sg3 opens the first rank: 2.Re1. The white rook is unpinned a fourth time with 1…Sd6 2.Rf5, which exploits the new guard of e7 by the a7-rook. There’s plenty of by-play in this impressive battery problem: 1…Sc5 2.Rxf7, 1…Bxe5+ 2.Qxe5, 1…Qxg5 2.Bxg5, and 1…gxh6 2.h8(Q).

Nigel Nettheim: The black pawn on a5 can be removed.
Jacob Hoover: What I liked about this problem is the multitude of themes illustrated (unpins, line-opening, and line-closing) and that the e5-rook, despite being pinned in the diagram, is the mating unit in four out of the eight variations. Masterful.

 
243. Andy Sag
Chess in Australia 1988
Helpmate in 4

Back in 1988 I proposed a tourney idea for Chess in Australia, in which every piece of a problem position must stand on its game-array square. This highly restrictive condition did not generate a sufficient number of entries for a tourney, but of the few examples that appeared, I liked Andy’s helpmate best. The solution is 1.Qc8 Sf3 2.Kd8 Se5 3.Kc7 Bf4 4.Kb8 Sc6. White sets up a battery to give a double-check model mate. The position is economical (nearly a miniature) with most pieces taking part in the play directly – only the d7-pawn is used as a plug to stop a dual.

 
244. Alexander Goldstein
Express Wieczorny 1954
2nd Prize
Mate in 2

White prepares an indirect battery on the b-file with 1.Qb8! (waiting). The key also changes the direction from which the queen controls b5, so that the potential mate Sc5 would not cause a self-interference. Now a random black queen move, 1…Q~, unpins the b3-knight and admits 2.Sc5. The correction move 1…Qxa3 self-blocks and leads to 2.Sc3 (when the white queen is needed to guard b4). Also, 1…Qxb3+ 2.cxb3. The black knight also enacts correction play; the random 1…S~ opens a white bishop line and allows 2.Sc3, while 1…Sd5 defends c3 but frees the b3-knight for 2.Sc5. The two pairs of thematic variations produce a reciprocal effect – the two white knights swap their roles in responding to Black’s random and correction moves.

Jacob Hoover: Note that if 1…Qxc2, the queen will be pinned by the d1-bishop after the knight moves. A lovely problem with a nice reciprocal theme seen with the knight mates.

 
245. A. Hackett
Town and Country Journal 1897
Mate in 2

A fine waiting key, 1.Qb1!, relinquishes the Q + S battery and gives the black king an additional flight. The three diagonal flight-moves produce 1…Kxc6 2.Qb7 – a switchback, 1…Kc4 Qd3 – a pin-mate, and 1…Kxe6 2.Bf7. Unusual for a multiple-flights problem, there are many good supplementary variations: 1…S~ 2.Qxe4, 1…Be~ 2.Rxd6, 1…Bd~ 2.Qa2, and 1…dxe6/dxc6 2.Qa2.

Jacob Hoover: Many variations deal with line-opening. Nothing really noteworthy about this problem aside from the plethora of queen mates, in my opinion.
Nigel Nettheim: Flights to 3/4 of a star (thus a thematic key); the captures by Black make up – or more than make up – for the star being not complete. Efficiently constructed with some very nice mates.

 
246. Gordon Stuart Green
The Problemist 1977
Mate in 4

If White protects the h3-knight with an additional piece, the g1-knight would be freed to give mate. This plan prompts two plausible tries and the key. The first try 1.Ke4? threatens 2.Kf4/Kf3 3.Kg4 and 4.Sf3. After 1…Bg5 (which answers 2.Kf3? with 2…Bxe3 3.Kg4 Bxg1), White continues with 2.Sxg5 Kxg1 3.Sf3+ Kf2/Kf1 4.Rb2. But Black cleverly escapes with a self-immobilising manoeuvre, 1…Bh4! 2.Kf4/Kf3 g5 3.Kg4 – stalemate! The second try 1.Bb7? threatens 2.Bf3 3.Bg4 and 4.Sf3. The stalemate defence wouldn’t work here because of the unblocked a-pawn, but now 1…Bg5! is effective because of 2.Bf3 Bxe3 3.Bg4 Bxg1 or 2.Sxg5 Kxg1 3.Sf3+ Kf2/Kf1. The key 1.Ke2! threatens 2.Kf3 3.Kg4 and 4.Sf3. If 1…Bh4 then 2.Rg5 forces 2…Bxg5 3.Sxg5 Kxg1 4.Sf3, a mate that relies on the white king’s position on e2 to control f2 and f1.

Jim Cannon indicates that the program Fritz 12 was unable to find this problem’s key, managing only to mate in five moves. But Jim’s son David Cannon (a top junior player) solved it successfully!

 
247. A. E. Ramsey
Check! 1945
Mate in 2

After the square-vacating key 1.Sc5!, White threatens 2.Re4. Black has two pairs of defences on e6 and b4, where each couple results in a mutual interference between two line-pieces: 1…Be6 2.Sc6, 1…Re6 Rxd5, 1…Bb4 2.Sb3, and 1…Rb4 2.Qxc3. Thus the Grimshaw theme is presented twice. The white queen does more work in the by-play, 1…Rd6 2.Qh4 and 1…Sd2/Sg3 2.Qxe3. Also, 1…Rg4 2.Sc6 and 1…Rxd7 2.Sb3. Most other moves by the key-piece contain multiple threats (e.g. 1.Sg5? threatens 2.Re4/Sf3/Qh4), but these are tries that fail to provide for 1…Bb4! And if 1.Sd2? to answer 1…Bb4 with 2.Sb3, then 1…Rb4! refutes since 2.Qxc3 is disabled.

Jacob Hoover: Not just one, but two pairs of Grimshaw interferences.
Nigel Nettheim: The mutual interferences on b4 and again on e6 are very nice.

 
248. Denis Saunders
U.S. Problem Bulletin 1987
Mate in 2
Twin (b) Rf1 to f8

The first part is solved by a waiting key, 1.Qxd3!, which offers the queen to both black knights. 1…Sf~ self-pins the f3-pawn and enables 2.Se2, while 1…Sb~ allows 2.Sd5. The black rook shows correction play: 1…R~ 2.Qxf5 and 1…Rxh5+ 2.Sfxh5, the latter an indirect battery mate. The two black pawn moves both open a line for the queen: 1…e2 2.Qd2 and 1…e4 2.Qd6. In part (b), the key 1.Sh7! involves a threat, 2.Bxg5. Now defences by the f2-knight are followed by a different mate: 1…Sh3/Se4 2.Qe4, which exploits the white rook’s pin of another f-pawn. More changed mates occur when Black moves the rook: 1…R~ 2.Rxf5 and 1…Rxh5+ 2.Sgxh5. Three good free changes are brought about in the two phases of play.

Jacob Hoover: Quite interesting that the pin is featured in both parts, but in different ways.
Nigel Nettheim: In (a), the capturing key is fine; the queen needs access to d2 and d6. In (b), the try 1.Sfe4? is well answered by 1…Sh3! Remarkably, both parts seem to be efficiently constructed.

 
249. Molham Hassan
“Newton’s Cycle”
OzProblems.com 2015
Mate in 2

The B + S battery on the long diagonal seems prepared to fire if Black captures one of the eight white units constraining the e5-knight, e.g. 1…Bxf3+ 2.Sxf3 and 1…Rxg4+ 2.Sxg4. But there is no set response to 1…Sxd3 or 1…Sxc4, where each defence removes a white pawn needed to control a flight. The key 1.Sb6! threatens 2.Sd7 and also guards c4 and d5; now 1…Sxd3 2.Sxd3 and 1…Sxc4 2.Sxc4 are possible. Five other capture defences are answered by the set battery mates – all return captures by the e5-knight. 1…Sxc6 2.Sxc6, 1…Rxf7 2.Sxf7, 1…Rxg6 2.Sxg6, 1…Rxg4+ 2.Sxg4, and 1…Bxf3+ 2.Bxf3. Together with the threat-move, these white mates complete a knight-tour that is well unified by the square clearance effects. There’s by-play with 1…dxe5 2.Bxe5, and a try 1.Sf8? (threats: 2.Sd7/Se6) Sxc4!

Composer: The eight moves of the knight represent the orbit of the Earth around the Sun. The black king, like the Sun it represents, is eccentric or not placed in the centre of the circle.
Nigel Nettheim: A satisfying complete cycle traced out by the e5-knight.
Jacob Hoover: This knight-wheel is just awesome in that, going anti-clockwise from the threat square, the thematic defences include first three knight moves, then a bishop move, then three rook moves. Very orderly.

 
250. Linden Lyons
Die Schwalbe 2012
Mate in 2

The key 1.Rc6! threatens 2.Qc3. Since the threat entails the queen unguarding e3, any move of the rook on that square would defend by creating a potential flight. A random rook move – effectively what would occur if the piece is simply lifted off the square – allows two possible mates, 2.Sce2 and 2.Qf4, and they are differentiated with 1…Re2/Rf3 2.Se2 and 1…Rxg3 2.Qf4. Three corrections by the rook prevent these secondary threats but allow other mates, due to the arrival effects of the rook: 1…Re4 2.Sf5, 1…Re5 2.Bb6, and 1…Re6 2.dxe6. The black queen initiates three variations, all based on unguards: 1…Qa3/Qc4 2.Rc4, 1…Qb3 2.Sxb3, and 1…Qb4 2.Qxb4.

Jacob Hoover: Square-clearing key, while the rook defences grant the black king a flight square.
Nigel Nettheim: The defences by the e3-rook and by the queen are handled with nice variety and no duals. The a5-rook might seem unneeded, but it prevents a dual after 1…Qa5.