Weekly Problems 2025-B

Both white knights will need to move in each twin – to guard flights and to give mate respectively – but one gets pinned if Black shifts the f7-rook or the e7-bishop to self-block on f6. In part (a), the thematic try 1.Rf6? Sf7 (unpinning the other knight) followed by 2…Sh4 fails only because Black lacks a waiting move (e.g. 2.Be~? checks). The solution switches the two knights’ roles and moves the black king to the square where it will begin in (b): 1.Bf6 Se7+ (unpinning the other knight) 2.Kg5 Sf3. In part (b), the solution of (a) becomes the thematic try, with 1.Bf6? Se7 and 2…Sf3 failing as there is no waiting move for Black (e.g. 2.Rf~? checks). The try from (a) now works as the solution, because the king starting on the “wrong” square allows a tempo to be spent on returning it to the “right” one: 1.Rf6 Sf7+ 2.Kf5 Sh4. Black’s tempo play is enhanced by the paradoxical twinning of the king. The self-blocking moves to f6 are also Grimshaw interferences that enable mates on f3 and h4, anticipating that the king’s move will unmask a line of defence.

Andy Sag: Looks easy at first glance but great care is necessary to avoid checks on the white king.
Satanick Mukhuty: A lovely juxtaposition of Grimshaw and Umnov! Funny how, when you place the black king on f5, it’s mated on g5 – and conversely, when you put it on g5, it’s mated on f5.

The out-of-play c8-knight has two natural tries that threaten 2.Rxd5. 1.Se7? handles 1…Bg2 with 2.Sxf5, but 1…Ra5! refutes, while 1.Sb6? meets 1…Ra5 with 2.Qc4, but 1…Bg2! refutes. The key 1.Rd7! threatens 2.Qe5+ Kc4/Kc5 3.Qxd5, against which the main defences seen in the try phases are playable. 1…Bg2 enables 2.Se7 with the threat of 3.Sxf5, which leads to either the self-block 2…Be4 3.Se6 or the switchback 2…Bh3 3.Rxd5. 1…Ra5 similarly allows 2.Sb6, threatening 3.Qc4, and this branches into the self-block 2…Rc5 3.Qe5 or the switchback 2…Ra4 3.Rxd5 (2…Rxb6/Rb4/Rc3 3.Qc3). Two elegantly matching variations illustrate the Swiss theme, a logical style idea that involves changing White’s threat. Initially, the thematic tries 1.Se7? and 1.Sb6? carry the threat of 2.Rxd5. But after the preparatory key 1.Rd7! enticing 1…Bg2 or 1…Ra5, the respective knight moves 2.Se7 and 2.Sb6 entail new threats – 3.Sxf5 and 3.Qc4 – that Black cannot parry without creating more weaknesses.

Andy Sag: Giving the queen access to e5 looks attractive but precise placement of the rook is required (1.Rd8? Rb7!). The need to delay correct use of the c8-knight to the second move (in the two main variations) is not so obvious.
Satanick Mukhuty: Interesting logical problem showing self-block decoys! Note that 1.Rd8? with the same threat fails to 1…Rb7!, pinning the white queen.
George Meldrum: The key rids Black’s annoying pin on the white queen with …Rb7.  The variety of possibilities the setting holds makes it more difficult to solve.

The starting position is a complete block where all possible black moves are given set mates: 1…e2 2.Qxe2, 1…B~ 2.Qc4 (1…Bc5/Bb6/Ba7 result in a dual, 2.Qc4/Rc3), 1…Bc3 2.Rxc3, 1…g5 2.Qf5, and 1…h6/h5 2.Qxg6. White has no waiting move capable of preserving the zugzwang, however; e.g. 1.Qe6? Bc3! The key 1.Rc4! grants a flight to the black king and threatens 2.Rxd4. Taking the flight with 1…Kxc4 permits 2.Qe2, which shows a transferred mate relative to the set variation 1…e2 2.Qxe2, while 1…e2 now produces a changed mate, 2.Qxd4. Another change follows a random move of the black bishop: 1…B~ 2.Bc2, exploiting the key-move’s vacation of c2 and obstruction of c4 (a dual still occurs in 1…Bc5/Bb6/Ba7 2.Bc2/Rc3). The correction move 1…Bc3 again forces 2.Rxc3. The uncommon block-threat type is demonstrated with a fine key, two changed mates, and one added variation.

Andy Sag: Nearly fell for one of the tries. The key grants a flight capture and initiates a few changed mates. Unfortunately, a few duals in both true play and set play noted.
Jacob Hoover: A rather easy solve. One try 1.Qe6? (waiting) removes the set duals and otherwise seems to preserve the block, but 1…Bc3! refutes.
Satanick Mukhuty: For Black’s every response, there is a mate prepared. Yet, surprisingly, the key is not a waiting move. A fine example – with an active sacrifice – of what, I believe, is known as the Block-Threat idea!
Bob Meadley: The try 1.Bxa5? is defeated by 1…Bc3. An unusual position with six black pawns and no white pawns. Lovely two-mover by J. J. O’K.
George Meldrum: Elegance in a lightweight setting by J. J. O’Keefe.

The black king has to relocate to a dark square, to be mated by either the bishop or the pawn supported by the bishop (a third option where the pawn mates while guarded by the king takes too long to organise). In the first solution, the king heads for c7 to prepare for a pawn mate on b6, meaning the white pawn must capture the four black pawns placed diagonally one by one. 1.Kc6 fxe3 2.Kc7 exd4 3.Bc6 dxc5 4.Sb7 cxb6. In the second solution, the king aims for f4 so that the bishop could mate on e3, and this time the four black pawns must be removed by the bishop in the opposite order. 1.Ke4 Bxb6 2.Kf4 Bxc5 3.Bf3 Bxd4 4.Se4 Bxe3. An amusing problem in which the thematic black pawns serve contrasting roles – first assisting with the white pawn’s moves, then hindering the bishop, but needing to be captured all the same.

Andy Sag: The two white units take turns in gobbling up the b- to e-pawn chain; meanwhile the black king moves twice and the a8-bishop and d6-knight set up self-blocks. Nice twin!
Satanick Mukhuty: Delightfully funny!
George Meldrum: A problem to put a smile on your dial.

White wants to force Black to fire the B + R battery, but an immediate 1.Sf4+? Rxf4+ isn’t mate because of the e8-rook. Two non-thematic tries threaten 2.Sf4+ by withdrawing the rook from the e-file: 1.Rd8? pins the d6-pawn but 1…Sxb4! creates a flight on c5, while 1.Rc8? pre-empts the knight defence but 1…dxc5! creates a flight on e4. The key 1.Se4! closes the e-file to threaten 2.Sf4+ again, and Black defends by also cutting off the white rook – 1…Se5/Se7 2.Sf4+? Kxe4. However, these black interferences with the rook are exploitable, since White can now move the key-piece on e4 without activating that rook. After 1…Se5, which also cuts off the h8-bishop’s access to d4, White avoids a self-interference with the queen, 2.Sc3+? Kd4; instead, 2.Sf6+ forces 2…Rxf6. Analogously, after 1…Se7, which cuts off the e8-rook’s access to e6, White avoids interfering with the other rook, 2.Sf6+? Ke6; instead, 2.Sc3+ forces 2…Rxc3. These two variations demonstrate a dual avoidance effect called the Java theme. By-play: 1…Sxb3 2.Qxb3+ Rxb3. Additionally, the set play of this problem involves a paradoxical element; at first 1…Se5 and 1…Se7 enable 2.Sf4+ Rxf4, yet after the key, these knight defences disable the 2.Sf4+ threat.

Andy Sag: The key must accomplish two objectives: (1) guard c5 in case of 1…Sxb4, and (2) prevent the e-rook from moving to e2. Took a long time to see that 1…Sxb3 is a variation, not a try refutation!
George Meldrum: The key move is not hard to find. The three extra variations are tricky.
Satanick Mukhuty: Interesting dual avoidance!
Bob Meadley: The key allows Black to play 1…Sxb4 as c5 is covered by the key-piece. I wouldn’t like to solve one of Edgar’s 3-move selfmates!

Shifting the white king to release the d5-rook will threaten two double-checking mates, 2.Rd8/Ra5, but Black refutes with various checks, e.g. 1.Ke8? Qa4+!, 1.Ke7/Kf8? Qb4+!, 1.Kg6? Qb6+! Alternatively, White may aim for a zugzwang by preparing for the queen defences that maintain the pin; 1.Rg4? Qc4/Qa2 2.Rg8, but 1…Qf3+! (likewise 1.Rh4? Qf3+!), 1.Ke6? Qc4/Qa2 2.Rf8, but 1…Qb6+! The key 1.Kg8! (waiting) does leave the rook pinned and again answers 1…Qc4/Qa2 with 2.Rf8. A random queen move that unpins the rook leads to 1…Q~ 2.Rd8/Ra5. These dual mates are separated in 1…Qb8+ 2.Rd8 and 1…Qb7 2.Ra5, but here the white moves are not double-checks but pin-mates where the rook and bishop exchange functions as the pinner and mating piece. Two more checking defences are handled precisely, 1…Qg3+ 2.Rg5 and 1…Qxd5+ 2.Bxd5. An aristocrat miniature with a subtle key, plausible tries, and intriguing battery variations.

Andy Sag: The key does not remove the pin and allows two additional checks, but for a miniature waiter there are many duals.
Jacob Hoover: Thematic content: Avoidance of self-injury, unpins, battery plays.
Satanick Mukhuty: Interesting miniature with good content.

The black rooks are holding off a bishop mate on b1 and a queen mate on b2. White can try to draw the defenders away from their ranks by threatening a bishop mate on the a2-g8 diagonal, but 1.Bf5? Re1!, 1.Bg6? Rf1!, or 1.Bh7? Rg1!, and Black hangs on. The key 1.Be4! keeps the d1-rook tied up protecting d5 and b1, and remarkably puts Black in zugzwang. In the three main variations, the h2-rook causes an anticipatory interference with its partner along various files. 1…Re2 2.Bf5 – White paradoxically attacks e6 only when it’s guarded, to threaten 3.Be6+ Rxe6 4.Qb2, 3…Rd5 4.Bxd5, against which 2…Rde1 is now ineffective; 2…Red2 still allows 3.Be6+ Rd5 4.Qb2. Similarly after 1…Rf2, 2.Bg6 threatens 3.Bf7+ Rxf7 4.Qb2, 3…Rd5 4.Bxd5, since 2…Rdf1 has been neutralised. And if 1…Rg2, 2.Bh7 threatens 3.Bg8+ Rxg8 4.Qb2, 3…Rd5 4.Bxd5, given that 2…Rdg1 fails to defend. Other moves by either rook result in short mates, except for 1…Rd3 2.Bxd3 (3.Bb1) Rc2 3.Bxc2 S~ 4.Bb1/Qb2. The knight blocks the g-file with 1…Sg3 (like one of the main lines), then 2.Bh7 threatens 3.Bg8+ Rd5 4.Bxd5, while 1…Sf2 enables 2.Qb2.

Andy Sag: The potential mates Qb2, Bb1 and by the bishop on the a2 to g8 diagonal make it easy to overload the rooks.
Satanick Mukhuty: Overall, an excellent lightweight problem on anticipatory interference. The solution is not that obvious either.
George Meldrum: Really hard to solve. Had Black been able to skip a move then it would not have worked but as it was then the two black rooks got in each other’s way. Found no problem with the short mates as the concept of the problem was clear.