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351. John James O’Keefe &
Frederick Hawes

Manchester Guardian 1955
Mate in 2

The square-vacating key 1.Qa6! grants a flight on d4 and threatens the double-check 2.Sc4. Any black move to d4 would defeat the threat, and four such defences err by opening white lines, besides blocking the flight. 1…Sfd4 2.Sf7 and 1…Rd4 2.Rf5 see White exploiting the opened lines of guard. In 1…Scd4 2.Qd6 and 1…d4 2.Qb5, White makes use of the lines directly in the mating move. Black plays twice more to d4 with the unguard 1…Qd4 2.Sg6 and the flight-taking 1…Kd4 2.Sd1. So an impressive total of six defences take place on the same square.

Andy Sag: The key stops 1…Rxa1, gives a flight and threatens double-check mate defendable by moving any of six pieces to d4. Four of these open lines to allow different mates; moving the queen unguards g6 and taking the flight unleashes the battery mate.
Nigel Nettheim: 1…dxc4 is unprovided, and the white queen escapes capture by means of the key, which is therefore not a strong point. As compensation, or more, the five occupations of d4 that prevent a double-check lead to nice variations.
George Meldrum: The position is ugly, I love it! The queen moves away from the centre of play and gives the black king a flight square. Bravo to the key move, and to the black hole on d4 to which dark matter is drawn.
Ian Shanahan: A “trying” problem! Clearly the white queen has to move (to avoid 1…dxc4), but where? A fine composition, with lots of intensive strategic line-play and an excellent flight-giving key by a famous Australian duo.
Jacob Hoover: The fact that all of the defences happen on the same square – even the by-play variations! – gives a high degree of unification to this problem.

352. Aleksandr Pankratiev
Australian Chess Problem Magazine 1994
Mate in 3

The key 1.Qh7! threatens 2.Qd3+ c4 3.Qxc4. Black's thematic units are the knights and c5-pawn, each of which prevents two of three potential mates: Sc7, Sd4, and Rxb4. When one of these black units moves to answer the threat, it unguards two mating squares, and White responds by checking on the third square that is still guarded twice. The check deflects the other two black defenders, forcing each to leave one mating square completely unprotected. 1…c4 2.Sc7+ [A] Sexc7 3. Sd4 [B] or 2…Sdxc7 3. Rxb4 [C]. 1…Sdf4 2.Sd4+ [B] cxd4 3.Rxb4 [C] or 2…Sxd4 3.Sc7 [A]. 1…Sef4 2.Rxb4+ [C] Sxb4 3.Sc7 [A] or 2…cxb4 3.Sd4 [B]. The recurrence of three white moves as second-move continuations and third-move mates produces a cyclic pattern. Specifically, this outstanding three-mover exemplifies cyclic overload.

Andy Sag: Black looks safe with the c5-pawn and two knights providing double guards on c7, d4 and b4 but one of these must move to defend the threat, allowing White to exploit the resulting overloading of defenders.
Jacob Hoover: Each of Black's three defences unguards two of three mating squares and in each case White decoys another guard with a sacrifice on the third square.

353. Joseph Wilhelm
Australasian Chess Magazine 1920
Mate in 2

The key 1.Qxb6! carries a threat, 2.Qxe6, which is met by any black knight move. The thematic piece causes two pairs of self-interferences with the rooks: 1…Sd4 2.Bxb4, 1…Sf4 2.Bxh4 (set 2.Qxh4), 1…Sd8 2.c8(S), and 1…Sf8 2.g8(S). Another two interferences which cut off the queen and bishop occur with 1…Sc5 2.Qd6 and 1…Sg5 2.Qf6. And two square-clearances result from capturing the pawns: 1…Sxc7 2.Qxc7 and 1…Sxg7 2.Rxg7. So a knight-wheel is produced. The by-play repeats a queen mate: 1…Qd6 2.Qxd6.

Jacob Hoover: Since we have eight possible knight moves and eight different mates, this is a knight-wheel.
Andy Sag: A classic knight-wheel with four symmetrical pairs of variations.
George Meldrum: At first sight Black’s defence looks rock solid. When scanning Black’s moves, the knight allows White to mate for all moves other that when moving to c5, c7 or g5. The knight hence draws attention to itself and helps the solver find the solution.
Ian Shanahan: A complete black knight-wheel. However, the symmetry here detracts, and the white force is rather strong for the effects shown.

354. W. E. Roberts
The Problemist 1969
Mate in 2

The black king has two flights on g2 and e3, both unprovided. There is a set variation for the e5-pawn – 1…exd4 2.Sxf2 – but the key captures that pawn to remove its control of the B + S battery: 1.dxe5! (waiting). Now 1…Kg2 enables 2.Sxf2 while 1…Ke3 self-pins the black bishop and allows the vertical R + S battery to operate: 2.Sd4. A random black bishop move that unguards d4, namely 1…Bd4/Bxe1, also permits 2.Sd4. Four corrections by the bishop generate a further mix of direct and indirect battery mates: 1…Bxg3 2.S4xg3, 1…Bxc5 2.Sxc5, 1…Be3 2.Sf2, and 1…Bxg1 2.Sxg1. The try 1.Kxe5? (waiting) leads to one changed mate, 1…Bxe1 2.Sf6, but 1…Ke3! refutes. The severely underused white queen could be replaced by a black pawn on g4, with no difference to the play except for the loss of the aforementioned set line, 1…exd4 2.Sxf2.

George Meldrum: The key move rids the pesky black pawn on e5, and vacates the d4-square needed for the knight in one of the variations. A number of reasonable looking first moves for White make the solution harder to find.
Andy Sag: Compact setting. The key leaves eight legal moves for Black, all answered by knight moves, mostly battery mates. The flight self-pins the bishop; I like that one!
Jacob Hoover: The king-flights 1…Ke3 and 1…Kg2 allow 2.Sd4 and 2.Sxf2, respectively; while these moves look like repeats of previously seen mates, they could be viewed as distinct mates because the king is mated on a different square.
Ian Shanahan: Finding the key took a long time. Batteries galore! However, the position is rather cramped and ugly – which seems to be a feature of Roberts' style.

355. Johann Seilberger
Chess World 1946
Mate in 2

The thematic key 1.Qd7! (threat: 2.Qxd6) unpins the black knight, which in turn pins the white queen by opening the diagonal for the f5-bishop. A random move by the knight loses control of the R + P battery: 1…S~ 2.b6. The knight has three correction moves, two of which unpin the white knight on c4: 1…Sc7 also interferes with the d8-bishop and allows 2.Sb6, while 1…Sc5 also self-blocks and enables 2.Se3. The third correction 1…Sd4 cuts off the black queen for 2.Re5 (which also follows 1…Qe5). The by-play consists of 1…Qxc4+ 2.dxc4, 1…Sxd7 2.b8(Q), and 1…Bc7/Be7 2.Se7.

Andy Sag: The sacrificial key unpins the e6-knight which then moves to pin the white queen. Knight moves to the c-file unpin the c4-knight. 1…Sd4 unguards e5 allowing a pin-mate. Other knight moves unleash battery mates. A great example of pins and unpins.
Ian Shanahan: Strategically, incredibly rich. The unpinning key, moves by the unpinned knight, and ensuing mates, show one of my own favourite themes – the Dalton II theme (also known as the Plant theme). This unpinned black knight also makes correction moves which unpin a white knight, harking back to the strategic fireworks of the Good Companions. So: an unpin-pin-unpin sequence.
George Meldrum: The setting appears to contain some froth, but the main lines of play initiated by the black knight on e6 produce some beautiful mates by White.

356. Thomas Denton Clarke
The Brisbane Courier 1918
Mate in 3

Black has two legal moves in the diagram, one with a set continuation: 1…d5 2.Kxd7 d4 3.Rc5. White must provide for the other black move, 1…Kd5, and remarkably the only way is 1.Bg2!, setting up a B + P battery. Now 1…Kd5 is answered by the sacrifice 2.Re3, which branches to 2…fxe3 3.f4 and 2…Kc6 3.Se7. The other variation is unchanged from the set play: 1…d5 2.Kxd7 d4 3.Rc5.

Andy Sag: It took a bit of lateral thinking to work out how to deal with the unprovided flight. The rook sacrifice on second move is a clever touch made possible by the key setting up a hidden battery.
Jacob Hoover: Battery-creating key.
George Meldrum: The a4-pawn suggests that the black king will wander towards it, and the white bishop on f1 looks unneeded – paltry clues to help unravel this puzzle. Very difficult to solve and requires an “aha” moment for the idea to surface. Wonderful key move.