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376. Arthur Mosely
Good Companions 1916
Mate in 2

Set mates are provided for all possible black moves: 1…R~ 2.Sd2, 1…Rxd3 2.Qe6, 1…Sb~ 2.Sc5, and 1…Se~ 2.Bxf5. White has no way of retaining all of the set play, e.g. 1.Kb8? Sc6+!, 1.Be6? Rxd3!, while 1.Rc3? (threatening 2.Qe6) fails to 1…Rxd4! The key 1.Qa3! (waiting) grants a flight on d3 but sets up a battery to answer 1…Kxd3 with 2.Sd2. The mate following the correction move 1…Rxd3 is changed to 2.Qxe7. The remaining play is unchanged: 1…R~ 2.Sd2, 1…Sb~ 2.Sc5, and 1…Se~ 2.Bxf5.

Andy Sag: Complete block with one post-key mate change and one added pure mate after flight capture. A try worth mentioning is 1.Kxb7? (2.Sc5) Rb1!, pinning the knight.
George Meldrum: A wonderful key move and after the black king captures the rook, White needs to cover five squares to provide a mating net.
Jacob Hoover: After the key, 1…R~ still allows 2 Sd2 but this time it's an indirect battery play, and the response to the correction 1…Rxd3 (still a self-block) changes to 2.Qxe7. White also has an answer for the flight that the key grants: 1…Kxd3 2 Sd2 (distinct from earlier due to being a direct battery play as opposed to indirect). A rather nice mutate with black correction in both the virtual and actual play.
Ian Shanahan: Fantastic flight-giving zugzwang key. I found this to be most difficult to solve. A concurrent changed-mate after 1…Rxd3. This problem is masterful – just as one would expect from Mosely.

377. George Sphicas
The Problemist 1989
Series-helpmate in 7

The black king could potentially be mated on many squares, but the shortest sequence involves placing it on e2 for a queen mate on c2. This scheme requires Black to promote various pawns to self-block on f1, e1, and f3. Further, since Black is initially in check, the first move has to be a promotion on c1, and the new piece must not interfere with the eventual mate. 1.c1(S) 2.f1(B) 3.e1(R) 4.Ke2 5.d1(Q) 6.Qd5 7.Qf3 Qc2 mate. When first published, this seven-move problem held the economy of length record for a series-helpmate showing the Allumwandlung theme. But subsequently the record of six moves has been achieved, which is the theoretical minimum (given that Black must make four promotion moves plus two queen moves – one diagonal and one orthogonal – to ensure that the queen couldn’t be replaced by another promoted piece). Thanks to Michael McDowell for pointing out the correct source of this problem.

Jacob Hoover: All of the possible promotions (knight, bishop, rook, queen) are seen here, so it's an Allumwandlung.
Andy Sag: A tough one to solve as there are 14 feasible squares for the queen to finish on and c2 was the 8th one I tried. I guess you call it an Allumwandlung as it uses all possible promotions.
Ian Shanahan: Seeing the name above the diagram, one expected the four promotions (AUW, here capture-free). The only blemish is the black king being initially in check, a necessary “trick” to force accurate move-order.

378. Denis Saunders
The Problemist 1990
Mate in 2

The key 1.Se7! concedes a flight on d4 and threatens a battery mate, 2.Rd6. This B + R battery opens twice more with 1…fxe3 2.Rg4 and 1…Rxd4 2.Re6. The e3-knight fires two batteries at once – directly with the e1-rook and indirectly with the f2-bishop – in 1…Sxe5 2.Sc4, and likewise in 1…Kxd4 2.S3f5 but the roles of the rear battery pieces are 
now reversed. There’s by-play with 1…Rxe7/Rd5 2.Qd5 and 1…Qxg6/Qf6/Qe6 2.Qxd3.

Jacob Hoover: With 1.Se7! White activates the B + R battery on the e4-h7 line to go with the R + S battery on the e-file.
Andy Sag: The key gives a flight and threatens a battery mate. The set half battery gives a strong clue. Four variations also involve battery mates, two with double-checks. Try 1.Sg7? Sxe5!
George Meldrum: The setting has enough clues for the savvy solver to find the key. Though the stylishness of the variations is just about enough to do your head in.
Ian Shanahan: Tremendous flight-giving key and a stunning variation after 1…Kxd4. Well constructed too. But very anachronistic for 1990: the Good Companions did this sort of thing, with even greater complexity, 70 years earlier.

379. György Bakcsi
Australian Chess Problem Magazine 1997
Mate in 3

The black king has two flights on d4 and e4, both unprovided. The sacrificial key 1.Sxf4! threatens 2.Sd3+ Qxd3 3.Qxe6. 1…Bxf4 leads to 2.Qxf6+ Ke4+ 3.Qe5 – a cross-check and pin-mate, and 2…Kd6 3.Qe7 – a switchback mate in which the h8-bishop controls e5 upon the removal of the f6-pawn by the queen. If 1…Qxf4 then 2.Qxe6+ Kd4+ 3.Qd6 – another cross-check and pin-mate, and here the e8-rook guards e4 thanks to the queen’s removal of the e6-bishop. And 1…Qe4 allows 2.Qxe6+ Kd4 3.Qc4, and again the e8-rook is activated, this time to cover e5. The flight moves 1…Kd4/Ke4 are answered by the knight threat but a different mate results: 2.Sd3+ Bf4 3.Rxf4. Three times the white queen captures a blocking unit and then opens a line for a white piece, acting as if it’s the front piece of an indirect battery.

Andy Sag: A great feast of pin-mates, cross-checks and indirect batteries.
Jacob Hoover: Indirect battery play in the threat. Direct battery plays by White and Black in the variations, and the white queen performs clearance moves.

380. Robert Lincoln
Australian Chess Problem Magazine 1997
Mate in 2

Initially the black king has three flights, only one of which has a set mate (1…Kd4 2.Qd3). The key 1.Rb3! (waiting) grants a fourth flight on e6 and sacrifices the rook. 1…Ke6 2.Qf5, 1…Kc6 2.Qb7, and 1…Kd4 2.Qd3 together form the Y-flights pattern, while 1…Kc4 also permits 2.Qd3. The remaining variations are as set: 1…S~ 2.Qe4 and 1…c4 2.Qd7. There are plenty of plausible tries: 1.Rc3? (threat: 2.Qd7) Kc6!, 1.Re4? (2.Qd7/Qb7) Kc6!, 1.Qg6? (waiting) Kc4!, and 1.Qe7? (2.Qxc5) Kc6!

Jacob Hoover: The sacrificial key 1.Rb3! completes the block. This problem becomes easy to solve when one realizes that the white rook isn't actually needed to perform any of the set mates.
Andy Sag: Neat miniature with sacrificial key providing for two of the three set flights and adding a fourth. All queen mates from five squares.
George Meldrum: The rook move helps provide for the king flights to c4 and c6. Amazingly no extra solutions are found with so many queen moves to try.
Ian Shanahan: The two unprovided flights really flag the key, but the suite of resulting mates are fine. Theme: three-quarters of a star-flight. There are five distinct variations, in miniature – a form Lincoln used to call a “five bagger”! It's a shame the composer passed away recently.

381. Joseph Heydon
Good Companions 1921
Mate in 2

The key 1.Kxe4!, by controlling d4, threatens mate with any opening of the R + S battery: 2.Sf~. Initially in a safe position, the white king has walked into ten possible checks, and all are met by different mates: 1…Qxe2+ 2.Se3, 1…Qd3+ 2.Sxd3, 1…Qc4+ 2.Qxc4, 1…Qxb4+ 2.Sd4, 1…Qxc6+ 2.Rxc6, 1…Sg3+ 2.Sxg3, 1…Sf2+ 2.Bxf2, 1…Sd6+ 2.Sxd6, 1…Re8+ 2.Se7, and 1…gxf5+ 2.Rxf5. Two non-checking defences prompt white mates already seen: 1…Rd1 2.Sd4 and 1…Rd8 2.Sd6. While the key-move provoking ten checks is impressive, the record for such a task is held by a two-mover by J. C. van Gool, in which the key enables 13 checks.

Andy Sag: The key creates an octuplet threat but invites no fewer than ten checks. Five threats are separated by black moves. Another five defend all threats.
Jacob Hoover: Incredibly, the key 1.Kxe4! invites an ungodly number of checks – ten, in fact! – to threaten a knight discovery on the fifth rank. Five of these checks force particular knight discoveries.
George Meldrum: This problem is one to just simply enjoy.
Ian Shanahan: The check-provoking key is ipso facto excellent, inducing many variations. My only regret is that not all eight threats are separately forced.

Andy Sag proposed to adapt the problem to separate all eight knight mates, and the best setting we came up with is shown below. It accomplishes the knight-wheel task, but at the cost of one of the thematic checking variations.

381b. Joseph Heydon
Version by Andy Sag & Peter Wong
Good Companions 1921
Mate in 2

The same king move now walks into nine black checks, the missing one being 1…gxf5+. We gain three battery variations to complete the knight-wheel: 1…Rg8 2.Sg7, 1…Rh8 2.Sh6, and 1…hxg2 2.Sh4.

382. Nigel Nettheim
The Games and Puzzles Journal 1987
Series-selfmate in 16

Typically in a series-selfmate, White finishes the sequence with a deflecting check that compels Black’s mating move. But here no such white checking move could be made to work, and instead White sets up a position in which the black mate is forced by zugzwang. First White promotes to a knight with the aim of blocking h7, which will cut off the black queen and give the white king access to h6: 1.e5 2.e6 3.e7 4.e8(S) 5.Sc7 6.Se6 7.Sf8 8.Sh7 9.Kh6. White then use the remaining units to self-block on g5 and h5, and at the same time complete the confinement of the black king: 10.Bg5 11.e4 12.e5 13.e6 14.e7 15.e8(B) 16.Bh5. And now Black has only two legal moves, either of which mates: 16…Qxg7/Qxh7.

Jacob Hoover: The idea of this problem is to restrict the movement of both kings and the queen as much as possible. The way to do this involves two underpromotions, one of which is an Excelsior.
Andy Sag: Promotions to queen or rook require the bishop to shield on f8, so any checking finale takes too many moves. A non-checking finale must confine the black king forcing the queen to move, so we have to look for a finale where the queen can mate from either g7 or h7. Checking avoidance by the promoted knight leaves only one route to h7, so well done Nigel!
Ian Shanahan: An elegant miniature with well-motivated move order, particularly in regard to the promoted knight’s wanderings. Whilst White’s non-checking final move is subtle, Black’s dualized mate is a weakness.
George Meldrum: Nigel’s problem is neat and concise, requiring a very methodical move order.

383. Gordon Stuart Green
British Chess Federation Tourney 1954
4th. Hon. Mention
Special British Prize
Mate in 2

Two important set variations are 1…Se5 2.Bxb4 and 1…Sfd4 2.Re3. The thematic key 1.Rxb4! exposes the white king to numerous checks on the long diagonal, and threatens 2.Sd5/Se4 by guarding b3. 1…Se5+ results in a changed mate, 2.Re4, while 1…Scd4+ self-blocks and permits a different opening of the B + R battery: 2.Rb7. The remaining discovered checks by the c6-knight are handled by the threats, and in particular 1…Sxa5+ 2.Sd5 and 1…Sxb4+ 2.Se4 separate them. 1…Sfd4 2.Rb3 shows another change from the set play, and represents a third opening of the white battery. There’s by-play with 1…Sg7 2.Rxg3.

Andy Sag: The key creates a double-threat and sets up an additional battery which comes into play on three occasions, one being a switchback.
Jacob Hoover: Black defends by blocking the c3-h8 line. Two of these defenses (1…Se5 and 1…Scd4) fire the black battery on the long diagonal, a battery play which White counters with more battery play. A third knight defense (1…Sfd4) allows mate by a different double-check.
George Meldrum: The crisscross of play is amazing; the play after 1…Scd4/Se5 is insane.
Ian Shanahan: Cross-checks and batteries à la Mansfield. The key sets up a battery, at the same time opening a black battery directed at the white king. Then… fireworks. Beautiful!

384. Alex Boudantzev
The Problemist 1977
3rd Commendation
Mate in 2

The thematic try 1.Qb4? threatens 2.Qc3 (guarding d3, an unprovided flight). Three variations result: 1…Bd2 (opens the g3-rook’s line) 2.Qc5, 1…Sb5 (self-interference) 2.Qxc4, and 1…Kxd3 2.Qd2 (pin-mate), but 1…Re4! subtly refutes by shutting off the h1-bishop. The key 1.Qf3! threatens 2.Qxe3. A random move by the e3-bishop, 1…B~, enables 2.Qf6 – a changed mate with respect to 1…Bd2 in the virtual play. The correction 1…Bf4 is a self-interference that permits 2.Qe4 (or 1…Re4 2.Qxe4). The flight-move 1…Kxd3 produces a concurrent change, 2.Qd1 – still a pin-mate. Lastly, 1…Re7 is met by 2.Qd5. The correspondence between try and key is striking: the queen on the try-square b4 delivers various mates supported by the a5-bishop and a4-rook, and likewise on the key-square f3 the queen gives mates that require protection by the g3-rook and h1-bishop.

Andy Sag: The key provides for the flight-capture which results in a neat pin-mate.
Jacob Hoover: In all phases of play every mate (including threats) is performed by the queen, so we have the “girl power” theme here too.
Ian Shanahan: The unprovided flight-capture is a blemish, but the idea here – known as the Barnes I theme – is to position the white queen at the intersection point of a white bishop and rook, so it can move along their lines of guard, laterally and diagonally. The try's refutation took time to spot. The pin-mates after the flight are delicious.

385. Peter Wong
feenschach 1995
1st Hon. Mention
Helpmate in 2
Twin (b) Pd3 to b3
(c) Pd3 to a7
(d) Pd3 to d7

The black king on its initial square has too many flights to be covered, so it needs to move to a more confined position. On d4 it could be mated by …Sxe6 – which opens the R + S indirect battery to control the c-file – if e3 is blocked by the queen. But after 1.Kd4?, White lacks a waiting move that would allow this plan to proceed. So Black plays the self-block 1.Qe3 first in order to free the white king to make a tempo move: 1…Kh2!, and then 2.Kd4 Sxe6. Similar tempo strategy occurs in the remaining three parts when the d3-pawn is shifted to other squares: (b) 1.Ra3 Kxf2! 2.Kb4 Sxa6, (c) 1.Rb7 Kg1! 2.Kb6 Sa8, and (d) 1.Se7 Kg3! 2.Kd6 Se8. The four black king moves form a star pattern, while the four white king moves produce a cross.

Andy Sag: Not a twin but a star quadruplet. In each case, Black prepares a self-block and simultaneously allows the white king a tempo move, then the black king moves allowing the c7-knight to mate using an indirect battery to confine the king.
Jacob Hoover: In each solution Black's first move is a distant self-block that also allows White to move the king (because that is the only way White can avoid messing up the configuration of the other pieces). The four white king moves form a king-cross and the four black king moves form a king-star. Very nice. I love it.
Ian Shanahan: Black king star-flight and white king cross. Excellent! Criticism: in each phase, there's a lot of idle ebony.
George Meldrum: The confinement of the white king is not immediately obvious to be part of the main play. The solutions are both amazing and funny at the same time.

386. Cornelius Groeneveld
Australian Chess 2004
Mate in 2

In the diagram, Black’s only mobile unit is the d7-knight and any of its moves would allow 2.Qxc5. White has no way of maintaining this block position, however. The key 1.Qd8! (waiting) prepares an ambush behind that knight and unpins the other one on c5. Now 1…Sd~, besides unguarding b6, enables the queen to control d6 for 2.Sb6. The c5-knight yields two variations: the random move 1…Sc~ admits 2.Qg8 and the correction 1…Se6 prompts 2.Be4. Hence this is a mutate that effects one changed and two added mates.

Andy Sag: A complete block in a Meredith setting. The key unpins the c5-knight and changes the set mate.
Jacob Hoover: The c5-knight exhibits correction play; a random move of this knight loses control of the d5-g8 line while the correction move self-blocks.
George Meldrum: A clinical setting requiring a clinical approach to solving. Positives include: all new mates, delivered by queen, bishop, and knight, not just by the queen as in the set play; a nice key.
Ian Shanahan: A sweet mutate (with only one mate changed) after an unpinning key. The unpinned knight shows secondary black correction.