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326. David Shire
Australian Chess 2007
Mate in 2

The key 1.Rg4! protects e4 to create the threat, 2.Sb4. The variations 1…Re5 2.Sf6 and 1…Bc6 2.Sc7 show excellent, analogous play. In each case Black shuts off a white piece – the h8-bishop or the c8-rook – so that the threat-move, which interferes with the white queen, would give a flight on the fourth rank; but each defence also self-blocks, enabling a knight mating move that disrupts a line controlled by the same white piece cut off by Black. In 1…Rxh8 2.Rg5 and 1…Bxc8 2.Qxb5, Black removes the white line-pieces altogether but exposes the king to orthogonal mates on the fifth rank. 1…Sc2 2.Qxb3 and 1…Sd3 2.Qd4 see the black knight interfering with the queen on d1 twice to permit queen mates. The problem hence presents three pairs of corresponding variations. There’s by-play with 1…Ba3 2.Sxc3, 1…Rxe4 2.Qxe4, and 1…Qd4 2.Qxd4.

Andy Sag: The key guards the e4-knight threatening 2.Sb4 and leaves the queen en prise but frees it up to mate in four variations.
Jacob Hoover: In the diagram, the white queen – the only piece guarding the e4-knight – is threatened with capture by the b5-pawn. Of the squares near the black king that the white queen guards, all of them, with the sole exception of e4, are guarded by other white units. So the solution seems to be to put another guard on e4, and doing so also threatens 2.Sb4.

327. Frederick Hawes
British Chess Problem Society Tourney 1943
1st Prize
Mate in 3

The black knight has four legal moves including two checks, all with set play prepared: 1…Sb6+ 2.Qxb6 and 3.Qb1/Qb2/Qc5/Qc7; 1…Sc5+ 2.Qxc5; 1…Sb2 2.Qc5+ Sc4 3.Qxc4; and 1…Sc3 2.Qc5 and 3.Qa3/Qxc3. The key 1.Qg4! entails a short threat, 2.Qd1, and completely changes White’s answers to these defences. 1…Sb6+ 2.Kd6 (threat: 3.Qd1) Sc8+ 3.Qxc8, or 2…Sc4+ 3.Qxc4. 1…Sc5+ 2.Kc8 and 3.Qd1/Qc4. 1…Sb2 2.Qe2 and 3.Rc2. After 1…Sc3, not 2.Qc4? Qxg7! but 2.Qb4 (threats: 3.Qa3/Qb2/Qxc3) Sa4/Sd1 3.Qb1. In response to the knight checks, White makes a leisurely king move and, in the case of the first variation, invites two further checks!

Andy Sag: The threat is a short mate but we have all four possible knight moves providing a defence; the first variation involving successive checks is the highlight.
Jacob Hoover: After 1..Sb6+ and 1…Sc5+, if White moves the king anywhere other than the noted squares Black has a delaying check.

328. Edgar Bettmann
Henry Wald Bettmann &
Jacob Bettman

South Australian Chronicle 1883
Mate in 2

Set mates have been arranged for every possible black move: 1…d3 2.Qxd3, 1…e4 2.Qd6, 1…Ke4 2.Qf3/Qg2, 1…B~ 2.Bxb7, and 1…S~ 2.Sxf6. But White has no way of preserving all of these variations, e.g. 1.Qh2? d3!, 1.Qh3? e4! The withdrawal key 1.Qe1! (waiting) yields three new mates: 1…d3 2.e4 (nice en passant avoidance), 1…e4 2.Qxa5, and 1…Ke4 2.Qh1. The remaining play is unchanged: 1…B~ 2.Bxb7 and 1…S~ 2.Sxf6. The only flaw of this well-keyed mutate is the set dual, 1…Ke4 2.Qf3/Qg2, fixable by adding a white pawn on h2 and a black one on h3.

Andy Sag: Looks like an old classic; complete block with five variations including three changed mates.
George Meldrum: The range of tries, and the changed mates, combined with the innocuous looking key move make this a pleasing problem.

329. Arnoldo Ellerman
The Brisbane Courier 1919
1st Prize
Mate in 2

After the key 1.Qb2!, White threatens 2.Qg7/Qh8. Black has three defences on c3 that interfere with the b3-rook and unpin the white bishop on the third rank. This bishop is thus allowed to fire the R + B battery, playing to a different square each time to shut off a black line-piece. 1…Sc3 2.Be1, 1…c3 2.Bf4, and 1…Bc3 2.Be5. The direct unpin 1…Rxb2 enables the battery to fire one more time – 2.Bf2. A fourth defence on c3 sees the black rook closing one white queen line and opening another: 1…Rc3 2.Qb8. Lastly, 1…Rxg3+ permits 2.Rxg3.

Andy Sag: Sacrificial key and six variations, four involving different placements of the unpinned battery trigger bishop.
Jacob Hoover: A nice presentation of a line-effect theme. We also see a "defences on same square" thing going on.
Nigel Nettheim: Nice handling of the four defences on c3.
George Meldrum: An alluring setting with a wicked key move that provides threats by the double. But it is all in the variations, most of which centre around blocking the queen’s path on c3. My favourite is 1…Rc3 2.Qb8.

330. Niharendu Sikdar
Australian Chess 2006
Helpmate in 7

This tough helpmate is solved by 1.d5 a3 2.d4 axb4 3.d3 b5 4.dxe2 b6 5.e1(B) bxa7 6.e2 a8(Q) 7.e3 Qf3. Both thematic pawns depart from their initial ranks and eventually promote, so the Excelsior idea is doubled. The unusual motive for the black promotion accounts for the difficulty. Black promotes not for the purpose of employing the new piece (e.g. to self-block), but solely to clear e2 for the e3-pawn. A bishop promotion is required since another piece on e1 would either check White or control the mating square f3.

Andy Sag: Not hard to see that the promoted queen could get to f3 in seven moves but only if the e4-pawn was not there. Working out how to deal with the e4-pawn took forever. A number of near misses in eight moves make this a very difficult and tantalizing problem.
George Meldrum: I can personally vouch that there are about 20 other ways to do this in eight moves. It took most of my Saturday, and it was only in the freshness of Sunday morning when it came into view. There is only one was to describe this problem: frustratingly good.