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451. John James O’Keefe
Die Schwalbe 1933
Mate in 3

The black king has a flight-move that’s provided for, though another strong defence, 1…Bxc2, has no set reply. The thematic try 1.Rb2? threatens 2.Rb8 but 1…Bb5! refutes, since 2.Rxb5 is stalemate. The key 1.Se4! threatens 2.Sc5 and 3.Sb6 (which 1…Bxc2 doesn’t handle). Black defends by capturing the offered knight, 1…Bxe4, and now that the bishop is decoyed to the long diagonal, White can proceed with the original plan, 2.Rb2 (3.Rb8), because Black’s substitute defence, 2…Bb7, carries the weakness of self-block, permitting 3.Sb6. This three-move miniature hence exemplifies the Roman decoy theme. The flight variation is unchanged from the set play: 1…Kb7 2.c8(Q)+ Ka7 3.Rc7.

Andy Sag: A tricky miniature with a sacrificial key. Nice try is 1.Sb3? Be4!
Andrew Buchanan: The d2-knight is so far from the action it looks like it must move as the key.
George Meldrum: The far outpost knight on d2 begs to play. First attempt is stopped: 1.Sb3? Be4! Surprisingly then the knight finds its way to e4 in face of the bishop.

 
452. Barry J. da Costa Andrade
Chess World 1949
Mate in 2
Twin (b) After key of (a)

The diagram position is a complete block, where most black moves permit a knight mate on d5 or g2. The black queen is unable to maintain its focus on these squares: 1…Q~file 2.Sd5 and 1…Q~diagonal 2.Sg2; there are no duals when the queen lands on either mating square – 1…Qd5+ 2.Sxd5 and 1…Qg2+ 2.Sxg2 – though 1…Qh8 enables both mates. The f8-knight and h6-bishop cannot avoid interfering with the queen: 1…Se6 2.Sd5 and 1…Sg6/Bg7/Bg5 2.Sg2. Only the h1-knight elicits a different mate with 1…Sf2 2.Qxf2, while a dual follows 1…Sg3 2.Qf2/Sg2. White has numerous tries that aim to preserve the block but are subtly defeated by the black queen. 1.Bb~? Qxa2! and 1.f6? Qg5! allow the queen to keep its focus on the mating squares. Also, 1.Bh5? Qg4!, 1.Kb6? Qg1!, and 1.Ka6? Qxa2+! Only 1.a3! (waiting) solves. The unusual twinning calls for the position after 1.a3 to be solved anew with White to play. Again this is a complete block situation that White wants to retain, and now 1.Ka6! does the job, given that 1…Qa2 no longer checks.

When this problem was originally published, Frank Ravenscroft pointed out that it could be extended to three parts by transferring the b2-bishop to f6 in the diagram. The new (a) position would then be solved by 1.Bb2!, leading to the initial setting. Here 1.Bb2! completes the block (by providing for 1…Qxa2), unlike the other keys which maintain an existing zugzwang.

Andy Sag: The keys preserve set play but there are two duals.
George Meldrum: The fun in this complete block position comes from finding out what does not work and why.
Andrew Buchanan: The core geometry is a duel between the e3-knight and g8-queen, over control of g2 and d5. 1.Kb6? allows the beautiful 1…Qg1! 1.Bh5? suffers 1…Qg4! cutting off access to f3. If the other white bishop moves then 1…Qxa2! covers both of the key squares.
Ian Shanahan: The first key is irreversible; the second doesn't work in the first part because of check. Focal theme, with play unchanged. Cute!

 
453. Herbert Ahues
The Sun-Herald 1961
3rd Prize
Mate in 2

The key 1.Sd7! attacks f6 and threatens a battery mate, 2.Bh6. By opening the long diagonal, the thematic key also permits the d4-knight to give various discovered checks. A random placement of this piece, 1…S~+, allows the a4-rook to guard f4 and so admits the cross-check, 2.Bf6. The black knight has two correction moves that disable 2.Bf6 by controlling the white R + B battery, but these defences interfere with a black line-piece and lead to other cross-checks: 1…Se6+ 2.g7 and 1…Sf3+ 2.d4. Only three variations and the two white diagonal batteries (both unusually employing a pawn as the front unit) fire just once each, but the strategic intensity of the play makes this a case of quality over quantity.

Andy Sag: The key allows battery checks, all defeated by cross-checks. Adding a white pawn on h4 would be a slight improvement as it would give a true changed mate (set 2.Be7) for random moves of the knight.
Jacob Hoover: The key activates the black B + S battery on the long diagonal… There is no distracting by-play.
George Meldrum: A high-quality problem that sticks to its theme. A very minor flaw with the dual after 1…Be4.
Ian Shanahan: The key clears the line of a black battery directed at the white king, Good-Companions style. Old-fashioned for the date of publication, but timelessly beautiful nevertheless.

 
454. Laimons Mangalis
Die Schwalbe 1953
Mate in 6

The black king, though trapped in the corner, is also well protected, ironically because White’s bishops and pawns create a barrier that prevents any direct assault by the queen. A delicate approach is required to get the queen through this barrier, as White steers the black pawn on c6 into clearing a path for the piece. 1.Qa6! cxb5 2.Kb4 bxc4 3.Kc3 cxd3 4.Kd2 dxe2 5.Ke1 exf1(Q) 6.Qxf1.

Andy Sag: The long pawn chain is an obvious clue. What the pawn promotes to is immaterial. A very amusing one-liner.
Jacob Hoover: The queen flies down the now-open a6-f1 line for the mate.
George Meldrum: Too easy reduces the smile factor, nevertheless cute.
Nigel Nettheim: Amusing! The f6-pawn can be removed, if the e3-bishop is shifted to d4 [stopping the cook, 1.Qh8 cxb5 2.Kb4 bxc4 3.Qc3, etc.].
Ian Shanahan: The solution is spotted immediately, but the ladder mechanism is cute.

 
455. Alexander Goldstein
British Chess Federation Tourney 1955
4th Prize
Selfmate in 2

If White shifts the queen from the f-file to another square where it doesn’t control Black’s R + B battery, 2.Be3+ will be threatened, forcing 2…Bxe3. The choice of 1.Qd7! is natural, half-pinning the two black pieces, but it’s not obvious how White should proceed when Black captures the c4-knight with either piece (to answer 2.Be3+ with 2…Ke5/Sxe3!). Each capture by the bishop or the knight leaves the remaining piece on the d-file pinned, after which White wants to incapacitate the capturer on c4 in order to force Black to open the battery through zugzwang. Now pinning the c4-piece with one of the white rooks seems to create an unwanted flight on the second rank and spoil the battery mate. But it turns out that White can make such a pinning move by cleverly exploiting the position of the c4-piece, which has inadvertently placed a guard on one of the rook-squares, allowing it to be unblocked. 1…Bxc4 2.Ra4 Bg~ and 1…Sxc4 2.Rb4 Bg~. One other defence, 1…Sf5, is met by a grab, 2.exf5 Bg~.

Andy Sag: Tries: 1.Be3+? Bxe3+ 2.Qf1, and 1.c3+? Kxd3 2.Qxd5+ Ke2!
Jacob Hoover: In each of the main lines the capturing unit guards the square that the pinning rook vacates.
George Meldrum: The composer has clearly hung signs over the two rooks and pawn in front of the white king saying, “Do Not Disturb”. Little wonder a solver may go into panic mode before finding that both rooks are needed in variations. Deceptively good.
Nigel Nettheim: It took me two attempts to find the play, with the attractive use of the white rooks.
Ian Shanahan: The key establishes a half-pin, after which the piece that moves is pinned in the thematic play, forcing the bottom-rank battery to open due to zugzwang. Pretty strategy.