Weekly Problems 2013-A

The key 1.Qf4! pins the e4-pawn to threaten 2.Sxg4+ Kxc4 3.Sxe5. The threat exemplifies a Siers battery, in which the front piece of a battery – the e3-knight in this case – gives a discovered check, and after a black king step, that piece plays again to deliver mate from another direction. The threat is stopped by any move of the unpinned e5-knight, which triggers five high-quality variations. 1…Sc6 is the “random” defence (in the sense that the move entails no effect other than to vacate/defend e5), allowing 2.Bxd5 (3.Qxe4) Bxd5 3.Rxd5. Two prospective self-blocks by the knight lead to new Siers battery mates: 1…Sxc4 2.Sxc2+ Kd3 3.Se1, and 1…Sd3 2.Sxc2+ Kxc4 3.Sa3. The knight also has two checks: 1…Sf7+ interferes with the g8-bishop, enabling the subtle 2.Kf6 (3.Rxd5) Sf~ 3.Qe5, and 1…Sf3+ permits 2.Sxf3+ gxf3 3.Qf6, a switchback mate.

Upper left: 1.Sc7 Sc3 2.Sa6 Rb5 (model mate). Upper right: 1.Bf6 Sc8 2.Bd8 Sd6 (model mate). Lower left: 1.Rb2 Rb4 2.Rc2 Rb1. Lower right: 1.g3 Rh2+ 2.gxh2 Sf2 (ideal mate). A quartet connected by the consistent white material, while Black alternates the pieces used besides the king.

Ian Shanahan and Michael McDowell point out that the lower right part is the stand-out position, because of its set play: 1…Rf3 2.gxh3 Rxh3. Not only does this set line end with an ideal mate (like the actual play), but the two phases together produce the Zilahi theme, i.e. the two white pieces exchange their functions of getting captured and giving mate. Furthermore, the Platzwechsel motif is seen in that the two white pieces end up swapping their positions!

A strong try 1.Sd6? entails multiple threats – 2.Sxc4, 2.Sxf7 and 2.Rf5, but fails to 1…Sxd6! The key 1.Sc5! threatens only 2.Sd7. 1…Rcxd2/Rxc3 opens a white bishop line to f5 and permits 2.Rf5. The other variations are straightforward unguards by Black: 1…Rgxd2 2.Bg3, 1…Qxe8 2.Bf6, 1…Sxc5 2.d4, and 1…Bb5 2.Rxe6.

The curious position has the black king enclosed almost totally by other black pieces, and it is solved by 1.Sg8!, which threatens 2.Sf6. The white royal battery opens four times with 1…Rxg8 2.Kh3, 1…Qc2+ 2.Kf1, 1…Bf~ 2.Kg3, and 1…e2 2.Kf2. The latter two defences are unblocks that create a flight, and so is 1…R~ which provokes 2.Qxd3.

George Meldrum: This week's problem looks incredibly appealing. The solution was a tiny bit disappointing but I am expecting too much from such a light-weight position(?).

Here’s an alternative setting of the problem that saves a black pawn but adds a variation. The key is now 1.Se8! with the threat of 2.Sd6. The play is similar to that in the original, except for an extra unblocking defence by the d5-knight, which gives 1…S~ 2.Sf6. The f7-pawn of the original can be removed, since its sole purpose was to prevent the d5-bishop from capturing the key-piece on g8.

After the key 1.Qc1!, White threatens the pin-mate 2.Qc4. Two defences on d6 unpin the d5-pawn, but cause a pair of Grimshaw interferences: 1…Rd6 2.Qf4 and 1…Bd6 (or 1…Rc6) 2.Sc6. A further seven variations show good variety of play: 1…Bc2/Ba2 2.Qxa1, 1…Bxd3 2.Rxd3 (changed from the set 2.Qxd3), 1…Se3 2.Qxe3, 1…Sd2 2.Qg1, 1…Qa2/Qc3 2.Qc3, 1…b5 2.Qc5, and 1…Re6+ 2.Sxe6. Including the threat, the white queen mates seven times from different squares.

The key 1.Sg2! has no threat but waits for Black’s e1-bishop and h1-knight to mutually obstruct each other: 1…Bf2 2.Be2 and 3.Bd3 since 2…Sf2 is no longer possible; 1...Sf2 2.Ra4 and 3.Rxd4 since 2…Bf2 is ruled out (2…Sb3/Sc4/Sf3 3.Bf3). A similar pair of self-obstructions takes place on g3: 1…Bxg3 2.Bg4 and 3.Bf5 – 2…Sxg3?? illegal; 1…Sxg3 2.Ra6 and 3.Re6 – 2…Bxg3?? illegal (2…Sc4/Sf3 3.Bf3). There’s by-play with 1…h5 allowing 2.Sf3 and 3.Sg5 (2…Sxf3 3.Bxf3), and short mates follow 1…d3 2.cxd3 and 1…Sd~ 2.Bf3.

A ‘random’ move by the e5-knight would threaten 2.Qd6, and two particularly interesting tries with additional threats are 1.Sxg6? (2.Qd6/2.Sf8) Sd7!, and 1.Sc6? (2.Qd6/2.Sxd8) Sb7! The key 1.Sf3! surprisingly grants two flights on the f-file and threatens only 2.Sg5. A pawn-Grimshaw occurs on f6 with 1…Bf6 2.Qh3 and 1…f6 2.Sxd4. A third interference on the same square is shown with 1…Kf6 2.Qe5, when the king cuts off the bishop. After 1…f5, the queen’s threat seen earlier becomes effective again: 2.Qd6. Lastly, 1…Kf5 is met by the battery mate, 2.Sg5.

The key 1.Kf6! covers e5 to threaten 2.Sde6. The black bishop on e4 defends by vacating that square as a potential flight for the king, and generates seven diverse variations. The Q + B battery is activated in 1…Bf3/Bg2 2.Bf3 and 1…Bf5/Bg6/Bh7 2.Bf5. Interfering with the c1-rook allows another white battery to fire: 1…Bb1 2.Rc2 and 1…Bc2 2.Rb1. Two self-blocks take place with 1…Bd3 2.e3 and 1…Bd5 2.Sxb5, plus a square clearance with 1…Bxc6 2.Sxc6. The latter error also occurs in the by-play, 1…Rxd2 2.Rxd2.

The key 1.Qh7! preserves the Q + R battery while threatening 2.Qe7+ Be6 3.Qxe6. Black has two knight defences to d3, self-blocking moves that free the c2-pawn to attack d4 or d5 and threaten a battery mate. The correct choice of white pawn move after each thematic defence is artfully determined. After 1…Scd3, White avoids 2.c4? with the threat of 3.Rxf4, because of 2…Rxf1!, allowing the king to escape to e3. Instead White plays 2.c3, and now 2…Rxf1 is ineffective against the threat of 3.Re5, which recovers e3 (2…Bxf5 3.Qxf5). After 1…Sfd3, not 2.c3? threatening 3.Re5, because of 2…Bxg1!, creating a flight on f3. Now 2.c4 is correct, and the threat 3.Rxf4 works against 2…Bxg1 by guarding f3 (2…Bxf5 3.Qxf5). Also, 1…Be6 2.dxe6 (threat: 3.Rc5, etc.) d5 3.Rxf4.

A good sacrificial key, 1.Sd4!, makes no threat. If Black takes the knight, White continues with another waiting move – 1…exd4 2.Sf4, leading to 2…d3 3.Bf6 and 2…e3 3.Qh7. If the king moves, a pair of echo mates follows: 1…Kh5 2.Sf5 and 3.Rg5; 1…Kxh3 2.Sf3 and 3.Rg3, while 2…exf3 permits 3.Qh7. The set play (surprisingly ruled out by the key) 1…d4 2.Qxe4+ Kh5 3.Qh7, 2…Kxh3 3.Qh7/Qh1/Rh1 could be made more accurate by transferring the f2-pawn to h2, so that 3.Qh7 is always forced.

A striking diagram in which the pieces seem to form an arrow shape. There are two similar tries: 1.Qd8? (threat: 2.Qh4) Rxd8 2.Rb1, but 1…Re7! refutes, and 1.Qa5? (2.Qe1) Rxa5 2.Rh7, defeated by 1…Rb4! The classic key 1.Qa8! (waiting) places the queen in a corner to ambush behind the two black rooks, and is also a double-sacrifice. 1…Rb~file 2.Qh8, 1…Rb~rank 2.Rb1, 1…Ra~rank 2.Qa1, 1…Ra~file 2.Rh7.

It’s a slight weakness that initially no mate is set for the checking defence 1…Sd4+, but the thematic key 1.Kb7! (threat: 2.Sc6) exposes the white king to various other checks instead. 1…f6+ 2.Se7 and 1…f5+ 2.d7 see White firing different batteries to exploit the black pawn’s self-blocks. A third check is an unguard that activates another battery: 1…Qb1+/Qb2+ 2.Bb6. Yet more battery play is shown in 1…Sd4 2.Bxf4 and 1…Se7 2.dxe7, to give a remarkable total of five thematic variations with no by-play at all.

White must release Black from a stalemate position, and the correct way is the delightful 1.Ra5! (waiting). Accepting the sacrifice, 1…bxa5, unpins the g5-pawn and White continues with another waiting move, 2.Be2, to prepare for the battery mate 2…gxh4 3.f4, and also 2…g4 3.fxg4, a model mate. If Black checks with 1…b5+, then 2.Bxb5 sets up another battery to answer 2…gxh4/g4 with the pin-mate 3.Be8.

In this pleasing mutate, every black move in the diagram already has a mating reply provided, but White has no simple waiting move. The key 1.Bf5! (waiting) changes one of the set mates from 1…e3 2.Bxf3 to 1…e3 2.c4. The key also generates a number of added mates by unpinning the g5-knight: 1…Sxe6 2.Bxe6, 1…Sh3 2.Bxh3, and 1…Sh7 2.Bxh7. The remaining lines are unchanged from the set play: 1…R~file 2.c4, 1…R~rank 2.Sxf4, 1…Rxc3+ 2.Sxc3, 1…Sb~ 2.Qc5, 1…a6/a5 2.Sb6, 1…fxe6 2.Bxe6.

After the key 1.Sg2!, White threatens 2.Qf4. Black has two thematic defences to e5, self-blocking moves that allow White to fire the B + S battery: 1…Be5 2.Sb4 and 1…e5 2.Se7. So each defence entails a black rook’s line-opening that must be countered by the white knight’s shut-off – vivid strategy. Two more self-blocks free the white queen to mate in other ways: 1…Rxf5 2.Qe3 and 1…Bf3 2.Qc2. Lastly, 1…Bc1/Bd4 permits 2.Rd4.

The four solutions are divided into two interrelated pairs. The first pair, 1.Be2 Kh3! 2.Re1 Ba4 and 1.c2 Kxg1! 2.Qe1 Bg4, has more thematic interest, showing white king tempo moves and different battery mates. The second pair, 1.Bb2 Ba4+ 2.Kc1 Rd1 and 1.Kc2 Bg4 2.Qb2 Bd1, sees the black king moving instead, with White giving different mates on the square initially occupied by that king. The two pairs of solutions are also loosely connected by the way the mating moves of the first pair recur as the opening moves in the second pair.

The thematic key 1.Kc4! self-pins the knight on d4 and threatens 2.Rb5. The knight is unpinned by 1…Sf4 which also cuts off the f5-rook, enabling 2.Sf3. Another unpinning move, 1…Se4, self-blocks as well and allows 2.Sc6. 1…Sf6 interferes with the other black rook to permit 2.Rxe6. The black queen has two defences – firstly another self-block on e4 that leads to a different mate: 1…Qe4 2.Qxb8, and secondly a check granted by the key: 1…Qxd4+ 2.cxd4. Also, 1…Bd6/Ba7 2.Bd6.

Set play is arranged for two prominent flight-taking moves: 1…Kd5 2.Qd3 and 1…Kf5 2.Qf3. The key 1.Sxg4! threatens an indirect battery mate, 2.Sf6. Now when the king moves, the set mates don’t work because the key-piece has lost control of c6 and g6. Instead the actual play is 1…Kd5 2.Qf3 and 1…Kf5 2.Qd3, demonstrating a reciprocal change of white mates with respect to the two defences. The new mates are possible because the key-piece has also opened two potential pin-lines on the fifth rank, besides removing the g4-pawn’s guard of f3. There’s by-play with 1…Sf3 2.Qf4.

If White tries 1.Ra3? to threaten 2.Ra8, Black refutes by playing 1…0-0! So White first executes a foreplan aimed at disabling the castling defence. The key 1.Rg7! threatens 2.Rc8 and forces 1…Kf8. The switchbacks 2.Rgc7 Ke8 bring us back to the original position, but with the difference that …0-0 has been made illegal. Now Black has no defence against the mainplan of 3.Ra3 and 4.Ra8. An attractive rendition of the theme, using merely seven pieces.

In this complete block position, every black move has been provided with a set mate: 1…Ba3/Bf8 2.Sf4, 1…Bh2/Bb8 2.Sdb4, 1…Sf~ 2.Qd2, and 1…Sb~ 2.Qc3. The key 1.Qf2! (waiting) disables all of the set play by abandoning the queen’s attack on d2 and c3. Now with the queen guarding e3 and d4, new mates are possible against the same defences: 1…Ba3/Bf8 2.Se5, 1…Bh2/Bb8 2.Scb4, 1…Sf~ 2.Qe3, and 1…Sb~ 2.Qd4. Furthermore, the key has enabled two additional variations: 1…e1=Q 2.Qc2 and 1…e1=S 2.Qxf1. This excellent mutate renders an uncommon complete change of play.

The e3-knight is prevented from giving mate by the pinning black queen, and the problem shows an attractive variety of ways by which the knight is unpinned. The key 1.Qf6! aims to divert the black queen with 2.Qa6+ Qa4 3.Sc2. After 1…Rg6, White can continue with 2.Ke2 and 3.Sc2 because the black rook has hindered 2…Bh5+??, and if 2…Qe5 re-pinning the knight then 3.Qxe5. The analogous 1…Rc6 enables 2.Kg2 and 3.Sc2 since 2…Bc6+?? is no longer an option. The black bishop in turn impedes the c8-rook with 1…Bc6 (also 1…Ra8) 2.Qxd4+ cxd4 3.Sc2.

The black king initially has a provided flight: 1…Kxe6 2.Qe7, but White disrupts this set line by playing 1.Qe7! immediately, with the threat of 2.Sexd4. The thematic key has allowed Black to check on the 4th rank, though a random move by the d4-knight fails to handle the threat. The correction 1…Sf3+ cuts off the g2-bishop and forces 2.Sf4. Two other correction moves abandon the black knight’s control of the R + S battery: 1…Sxe6+/Sc6+ 2.Sxh4. This battery fires again with 1…Re4 2.Sfxd4. Three more variations make up the by-play: 1…Sf4 2.exd4, 1…c6/c5 2.Qd6 and 1…Bf6 2.Qxf6.

If White has the move, there is a set mate in one: 1…d3. When Black plays first, every move will disturb this mate, but the two sides can bring it back by each performing a rundlauf or round-trip. 1.f3+ Ke1 2.f2+ Kd1 3.f1=R+ Ke2 4.Rf4 d3. We see three consecutive black checks, and good white-black interplay that determines the path of the triangulating king.

Ian Shanahan: It’s also an ideal mate.

The fine withdrawal key 1.Qa3! grants a flight and permits two black checks. The threat 2.Bd5 utilises the newly formed Q + B battery, which fires again in response to the checks: 1…Ke3+ 2.Bf7 and 1…c1=Q+ 2.Bd1. If 1…e3 then White exploits the opening of the diagonal with 2.Qxa8. Two quality cross-check variations, but it’s a pity that there’s so little by-play.

After the waiting key, 1.Qf4!, Black has eight possible pawn moves and each provokes a different queen mate. 1…cxb3 2.Qc1 (switchback), 1…c3 2.Qxb4, 1…d2 2.Qxc4, 1…cxb5 2.Qxc7, 1…cxb6 2.Qd6, 1…fxg5+ 2.Qxg5, 1…f5 2.Qe5, 1…gxh5 2.Qf5. Yet three more queen mates occur after the black bishop’s moves: 1…Bf2 2.Qxf2, 1…Be3 2.Qxe3, 1…Bd4 2.Qxd4 (1…Bh2 2.Qf2/Qe3/Qd4). In contrast to the previous problem, the emphasis here is on the quantity of variations, which reveal little strategy but possibly constitute a task record blend of black pawn defences and white queen mates.

The key 1.f4! threatens 2.Qf2+ Kxd1 3.Qd2. Five of Black’s defences commit the same type of error: the prospective self-block of a square not initially adjacent to the black king. 1…Rxf4 2.Rd2+ Kf3 3.Sg5, 1…Bxf4 2.Qf1+ Ke3 3.Qd3, 1…Bxd4 2.Qf1+ Ke3 3.Re1, 1…Sc4 2.Re1+ Kd3 3.Sxb4 (2…Kf3 3.Qg3), 1…Sxe4 2.Qf1+ Ke3 3.Rd3. Arguably 1…Rc2 is a sixth thematic defence even though it doesn’t stop the threat of 2.Qf2+, considering 2…Kxd1 3.Qf1 is a new mate that again exploits a distant self-block. Also, 1…Kf3 2.Sg5+ Kxf4 3.Rf1 or 2…Ke2 3.Qe1. The repetition of 2.Qf1+ is the only flaw in this remarkable problem, which shows great unity and is completely dual-free.