Weekly Problems 2011-B

The key 1.Sg7! (waiting) sacrifices the knight to all three black pieces, and allows the black king to discover check, though on the downside the move also restricts severely the movement of Black’s rook and bishop. 1…Kxg7+ 2.f8=S, 1…Kxe7+ 2.fxg8=S, and 1…R/Bxg7 2.Re8. Two pleasing knight promotions, especially in the first variation, which involves a cross-check and the Phoenix theme (promotion to the same kind of piece as one that was captured).

In the diagram, Black’s only mobile piece is the b1-bishop and any of its moves allows an immediate mate, 2.Qxe1. But without a waiting move capable of preserving this set mate, White is forced to extend the play to three moves, making this problem an example of a pseudo two-mover. The difficult key 1.Qc4! (waiting) frees the second bishop and sets up a half-pin on the first rank. 1…Be-any self-pins the b1-bishop, enabling 2.d4 and 3.Qxe2 (1…Bg3 2.d4 Bxh2 3.Rxb1). 1…Bc2 immobilises the e1-bishop, admitting 2.Qg8 and 3.Qg1. After 1…Ba2/xd3, the white queen gives a switchback mate, 2.Rxe1+ Kxe1 3.Qc1.

A good key 1.Qxc6! (threat: 2.Sf3) offers the queen and also allows two black checks on the long diagonal. 1…Rxc6 2.Sxc6, 1…Qd5+ 2.Qxd5, 1…Be4+ 2.Qxe4. Two related variations, 1…Qf5 2.Bc3 and 1…Rf8 2.Qc3, feature unguards from the rear that permit mates on the same square. The white queen delivers yet two more mates with 1…Ke5 2.Qxd6 and 1…d5 2.Qf6. 

Andy Sag points out that the problem can be improved by transferring the g6-bishop to c2 and the c6-pawn to g6, thereby avoiding the capture-key.

Initially the black king has two unprovided flights on f4 and e6. The try 1.Qd3? takes care of 1…Kf4 with 2.Qg3 but not 1…Ke6!, while 1.Kc6? covers 1…Ke6 with 2.Qd5 but not 1…Kf4! The key 1.Qb3! (waiting) removes the e6-flight but gives the king access to two new squares. 1…Kxd6 2.Qd5 (a mate transference relative to the try play of 1.Kc6?, when the same mate occurs against a different defence), 1…Kd4 2.Bf6, and 1…Kf4 2.Qg3.

Andy Sag: The key trades flights and adds a flight-capture.

The key 1.Bh5! crosses over the critical square g4 to prepare for a self-interference on that square. After 1…Ke3 2.Kf5 e4, Black has set up a potential stalemate. White answers by playing to the critical square, 3.Kg4, which closes the bishop line and grants Black a flight on e2. Now 3…Ke2 is forced, whereupon White mates by reopening the diagonal, 4.Kf4. An economical illustration of the Indian theme.

Andy Sag: Neat miniature one-liner.

A brilliant key 1.Bg5! yielding two flights seems to let the black king escape. There are two threats, 2.e3+ fxe3 3.Bxe3, 2…Kc5/Ke5 3.Bxe7, and 2.Bxf4 (3.e3 or Be3) Rb3 3.Sc2, 2…Rxd2 3.Sxb5. When Black takes the flights, the king walks into the battery formed by the key, 1…Kc5 2.Bxe7+ Kd4 3.Bc5, and 1…Ke5 2.Bxe7+ Kd4 3.Bc5. Two rook defences lead to mates given by the battery itself, 1…Rb3 2.Sc2+ Kc5/Ke5 3.Bxe7, and 1…Rxd2 2.Sxb5+ Kc5/Ke5 3.Bxe7. It’s curious how the white moves Sc2, Sxb5, and Bxe7 recur variously as second-move continuations and third-move mates.

Andy Sag: Well-constructed team effort. The key gives two flights leading to battery continuations.

Black has three possible moves in the diagram, all of which have been provided with a white mating reply: 1…Ka7 2.Qxb7, 1…b5 2.Qxb7, and 1…bxa5 2.Qxa5. The waiting key 1.Qa2! creates a Q + S battery and changes the responses to two of the black moves, 1…Ka7 2.Sc6, and 1…b5 2.Sc4, while 1…bxa5 2.Qxa5 is as set. The key also grants a flight, leading to 1…Kb5 2.Qc4. A light, classic mutate.

A fine key 1.Re5! (threat: 2.Sd3) shows a triple-sacrifice of the rook, including a flight offer. Taking the flight with 1…Kxe5 permits 2.Qxd6. The other captures on e5 result in self-blocks that White exploits, 1…dxe5 2.Qh6, and 1…Bxe5 2.Bd2. Two further variations see White recovering the e5-flight with the mating moves, 1…dxc5 2.Qf6, and 1…Sc1 2.Bg3.

A fairly obvious key, 1.Bd8! (waiting), prepares the white pawn to discover mate when the black queen moves: 1…Qd7/Qf7 2.e8=S, 1…Qxg6 2.e8=Q, and 1…Qxf8 2.exf8=S. The two battery pieces also seem to protect each other against captures by the queen: 1…Qxd8 2.exd8=Q, and 1…Qxe7 2.Bxe7. The black bishop illustrates correction play: 1…B-random 2.Sh7, 1…Bxf8 2.exf8=Q. Lastly, 1…S-any 2.Qe6. The white pawn delivers five distinct promotion mates, and it’s remarkable that every black queen move is followed by an accurate white mate.

Black begins: 1.Qd3 Rc5+ 2.Ke4 Rg4, and 1.Qe5 Kf3 2.Kd4 Rd2. White begins: 1.Rh3 Ke5 2.Kg3 Qf4, and 1.Rc1 Kd4 2.Rf1 Qe3. Two pairs of echoes, with three of the four parts ending in model mates. It’s a pity that the white pawn is required, being used only in one phase.

A terrific key 1.Sf7! provides three flights to the black king and threatens 2.Qd8. That White allows Black to castle as one of the flight-taking moves is quite unusual: 1…0-0 2.Sxh6. The king walks into another battery with 1…Kf8 2.Sfd6, while accepting the last flight leads to 1…Kd7 2.Qc6. There is only one by-play variation, 1…Be7 2.Qxe7.

A good sacrificial key 1.Rf2! entails the threat of 2.R4xf3. Two pairs of thematic variations follow. When the king captures either rook, the f3-knight becomes pinned by the remaining rook, and the queen exploits this with a pin-mate: 1…Kxf2 2.Qg1, and 1…Kxf4 2.Qg5. The f4-rook can also be captured by two other black pieces, resulting in self-blocks. Each blocking defence would apparently allow two white mates, but due to an additional line-opening effect, the dual is avoided: 1…Bxf4 2.Re2 (not 2.Sd1 because of the d8-rook), and 1…Rxf4 2.Sd1 (not 2.Re2 because of the a6-bishop). Lastly, 1…S-any also enables 2.Sd1.

Directmates of the ‘Bohemian’ style aim for a variety of elegant mating configurations, and this is a fine example. The key 1.Kg2! threatens 2.f4+ Ke4 3.Sc5, which is a model mate. Two more model mates are brought about with 1…Bd6 2.Sa5 B~ 3.Sc4 and 1…Ba7 2.Sb4 B~ 3.Sc6. Only 2…Kd4 3.Qf4 here is not quite a model, e4 being attacked by both the queen and the pawn.

The square-vacating key 1.fxg4! threatens 2.Rf3. Black defences on d6 remove the b8-bishop’s control of e5, but they cause a pair of Grimshaw interferences: 1…Rd6 2.Rf8 and 1…Bd6 2.Rxc4. An analogous pair of defences on d5, aimed at disabling the a8-bishop, generates another Grimshaw: 1…Rd5 2.Sxe6 and 1…Bd5 2.Sd3. Two further variations utilise the white queen: 1…Bxe3 2.dxe3 and 1…Rd3 2.Qf1. Finally, 1…Be2 also allows 2.Sxe6.

The waiting key 1.Qh1! surprisingly lodges the queen in a corner square, where the piece is also en prise. A random bishop move, 1…B~, permits 2.f4, while the correction move 1…Bxe4 enables 2.Qxe4. The black knight also produces correction play: 1…S~ opens the h-file for 2.Qh8, while the correction 1…Sg4 interferes with the black bishop, allowing 2.Qh5. The two black pawns open mating lines with 1…d3 2.Qa1 and 1…g2/gxf2 2.Qxh2. The active white queen delivers five mates and visits three corners, showing good long-range play.

The key 1.Rh3! vacates g3 to threaten 2.Sg3. Since the threat cuts off the key-rook's control of the third rank, any move by the f3-bishop would defend, by creating a potential flight. However, when it lands the bishop finds itself interfering with other black pieces: 1…Bc6 2.Sxc3, 1…Bd5 2.Sd4, and 1…Be4 2.Re3 – three nicely matching variations. The bishop provokes two more mates with 1…Bg4 2.Qxg4 and 1…Bh5 2.Qxh5. Also, 1…Qxf5 2.Sxc3.

Set mates are provided for all of Black’s moves in the diagram: 1…e6/e5 2.Rxg5, 1…f3 2.g4, and 1…R-any 2.Qe4. The thematic try 1.Se4? (waiting), which grants a flight, changes the mates to 1…e6 2.Sd6, 1…f3 2.S4g3, and 1…R-any 2.Rxg5. If 1…Kxe4, then 2.Bg6, but 1…e5! defeats the try, since the unpinned b5-knight prevents 2.Sd6. The key 1.Bc7! (waiting) introduces further changed play with 1…e6 2.Bg6, and 1…e5 2.Qc8. 1…f3 allows an unfortunate dual, 2.Sg3 or 2.g4, while 1…R-any 2.Qe4 is as set. An unusual mutate that includes an additional try phase besides the set and post-key play.

A fine key, 1.Sf7!, offers two flights to the black king, and also disrupts a set line, 1…h6/h5 2.Bg6. The threat is 2.Sh6, an indirect battery mate. Taking either flight allows the same queen mate, though the two variations are distinct given that the king is mated on different squares: 1…Kg6 2.Qg5, and 1…Kg4 2.Qg5. Three other defences by various black pieces are connected by the self-blocking error that each commits: 1…Sg4 2.Sd6, 1…Qf4 2.Qxe6, and 1…Be4 2.Qg5.

The diagram is solved by 1.Bg5 Rc7 2.Bc1 Rb8, and part (b) by 1.Bg6 Rb7 2.Bb1 Rc8. Coordinated black and white half-pin play. The black half-pin on the h-file leads to the pin of each bishop, exploited in the eventual mate. White similarly self-pins each rook with the initial move, but it is unpinned by an interposing black bishop, freeing the piece to give mate.

Nigel Nettheim: A bishop will unpin a rook. Simple but elegant.

This problem took part in a theme tourney that stipulates the key to be a queen sacrifice, and it's a striking example with 1.Qe6! solving. After this waiting key, captures of the queen and two other black pawn moves produce a quartet of “open-gate” variations: 1…dxe6 2.Rd8, 1…fxe6 (or 1…fxg6) 2.Rf8, 1…d6 2.Qxc8, and 1…f6 2.Qxg8. Three other defences are more straightforward unguards: 1…Bb7 2.Qxd7, 1…Sxg6 2.Qxf7, and 1…Sg~ 2.Sf6. Lastly, the correction move 1…Sxe7 permits 2.Qxe7.

A surprising key 1.Qf1! relinquishes the queen’s control of the b-file and yields a flight on b7. The threat is 2.Bd5+ Kxd5 3.Qc4, against which Black has only two defences. The main one 1…Kxb7 provokes the marvellous 2.Qxa6+, with three sub-variations: 2…Kxa6 3.Sc5, 2…Sxa6 3.Bd5, and 2…Ka8 3.Sb6. The second defence 1…f2 is answered by the more ordinary 2.Qxh1+ f3 3.Qxf3.

The key 1.Qc5! cuts off the a7-bishop and threatens 2.Rxd4. The thematic knight on d4 has six possible moves, and each one induces a different mate: 1…Sb3 2.Qxc2, 1…Sb5 2.Qxc6, 1…Se2 2.Re3, 1…Se6 2.Qe5, 1…Sf3 2.Sf2, and 1…Sf5 2.Sf6. All of these defences commit the error of self-interference – a good connecting motif. There’s by-play with 1…Bxc5 2.Sxc5, 1…cxd6 2.Sxd6, 1…Qe5/Qxd7 2.Qe5, and 1…Rd1 2.Re3.

The unprovided flight 1…Kc4 is a significant clue, since any potential key must deal with this strong defence. 1.Qg4! sets up an indirect battery on the fourth rank, and threatens 2.Sf6. 1…Kc4 walks into the battery directly and enables 2.Sc3. Taking the second flight on d4 (released by the key) permits another battery mate, though it’s the same move as the threat: 1…Kd4 2.Sf6. Black self-blocks in the variations 1…c4 2.Qd7 (changed from the set 2.Qe5), and 1…Rd4 2.Qe6. Also, 1…Rxe4 2.Qxe4, and 1…Bc3 2.Sxc3.

The diagram is a complete block, with every black move having a set mate: 1…R~rank 2.Sf6, 1…R~file 2.Sc3, 1…S~ 2.Qe5, and 1…c6 2.Sd6. Tries that attempt to preserve all of these variations fail, e.g. 1.Kd8? Rd3!, and 1.Ba7? c5! The waiting key 1.Se7! abandons two knight mates, but by putting an extra guard on f5, enables the queen to handle the black rook instead: 1…R~rank 2.Qf5, and 1…R~file 2.Qe3. The correction 1…Rf4 allows yet another queen mate, 2.Qd5. The remaining play is unchanged from the set: 1…S~ 2.Qe5, and 1…c6 2.Sd6. An exemplary mutate.

The two solutions of this miniature are 1.e1=Q+ Kxf3 2.Qb4 Ke2 3.Qb1 Sd3, and 1.e1=B Sg4 2.Kd1 Kd3 3.c1=R Se3. The first phase shows a paradoxical black queen promotion, and ends with an ideal mate, while in the second part Black underpromotes twice, to avoid attacking the white king or the knight’s mating square.

The key 1.Bh7! forestalls a black check on the h-file, but makes no threat. A nice variety of play follows the black rook’s defences. 1…Rh8 2.Qa1+ Kb8 3.Qxh8. 1…Re8 2.Qa4+ Kb8 3.Qxe8. 1…Rg8 2.Bxg8 Kb8 3.Qd8. 1…Rf3+ 2.Qxf3 Kb8 3.Qf8. 1…Rc8 2.Qa1+/Qa4+ Kb8 3.Qa7. Other rook moves permit short mates, while the king defence enables another fork by the queen: 1…Kb8 2.Qd6+ Ka8 3.Qxf8, or 2…Kc8 3.Qc7.

Andy Sag: Nice miniature waiter with many variations despite a few unavoidable shorts and minor duals. Well done, Arthur!