World Solving Championship – solutions (1)

39th World Chess Solving Championship – solutions

By John Nunn

Vasil Markovtsy, idee & form 2002

White to play and mate in two

The first thing to attract one’s eye is the arrangement of pieces along the sixth rank, called a half-pin. If one of the black bishops moves then the other one will be pinned and White should be able to exploit this. Such an arrangement exists in the diagram as a move by the e6-bishop is met by 2 Qxe7# (except for 1...Bd7 2 Qxd7#) and a move by the f6-bishop by 2 Qd7#. However, White has to make a threat or else Black can just make a rook move. So 1 Qa7 appears natural, intending 2 Qc5#, and meeting 1...Bxb3 and 1...Bd4 with the already prepared mates. However, 1 Qa7 fails to 1...f4! so something else is required.

The only difficulty in solving this problem is the psychological block against giving up the pre-existing arrangement and substituting a new one. However, experienced solvers know that this is exactly the sort of thing composers like to do, and so they will tend to look for this type of change. The key move is the spectacular 1 Qb5!, again threatening 2 Qc5#, but this time arranging to meet 1...f4 by 2 Ne4#. The mates on d7 and e7 has been surrendered, but are replaced by the new mates 1...Bxb3 2.Qe5# and 1...Bd4 2.Qd5#. The final variation is 1...axb5 2.Nxb5#.

Uri Avner & Shlomo Seider, Die Schwalbe 1987

White to play and mate in three

When solving a mate in three, it sometimes helps to try threatening an immediate mate and working out why that fails. Here White can try 1 Nxg6, intending 2 Qxe7#, which can only be met by 1...Kxd7, when the black queen defends e7. If the black queen’s defence of e7 could somehow be invalidated, then Nxg6 would work.

Solving is often not about analysing moves, but about putting together little clues in the position. It’s obvious that White’s second move must carry a threat since there is no question of zugzwang here, and in a three-mover it often helps to determine if this threat is likely to be a check or a quiet continuation. Three-movers with quiet second-move threats are generally harder to solve. Here there aren’t many ways Black can check in two moves (usually the determining factor) – indeed 1...Rf2 and 2...Rxf8+ or 1...Rh2 and 2...Rh8+ are the only ways. So the jury is out on that one – the threat might be a check, or it might be a quiet move with the first move providing a checking response to the black rook moves.

Other little clues are the strong defence 1...Qxc4, which White’s first move must provide a response for, the somewhat out-of-play bishop on g1 and the mysterious pawn on c2 which has no obvious function. At this point my eye was attracted to the move 1 d5, mainly because it enables White to meet 1...Qxc4 by 2.Rxe6+ Kxd5 3.Qe5#. It also allows moves such as 1...Rf2 or 1...Rh2 to be met by 2.Rxe6+ Kxd5 3.Qd4#. This all looks promising, but it’s still not obvious what the threat is. It took me a few minutes to notice that 1.d5 threatens 2.Ree4, intending 3.Qe5#, and if 2...Rxd5 then 3.Rxe6#. The rook has to go to e4 because (amongst other reasons) White needs to cover c4 after 2...Kxd5 3 Qe5#. Confirmation that this idea was correct came when I realised that without the c2-pawn 1.d5 could be met by 1...Bb1!, making ready to take the rook on e4.

It remained only to systematically check for Black moves that defeated the threat, and in addition to the rather dull lines 1...Qxc4 (or Bxc4) 2.Rxe6+ Kxd5 3.Qe5#, 1...Qa5 (or 1...Qb5) 2.Nxg6 and 3.Qxe7#, 1...Re2 2.Rxe2 (threat 3.Qe5#) 2...Kxd5 3.Qd4#, 1...Rf2/g2/h2 2.Rxe6+ Kd5 3.Qd4# there are the two lines which comprise the main point of the problem. Either move of the c7-pawn defeats the threat because then 2.Ree4 can be met by 2...Kxd5 and the b8-bishop stops the mate on e5. It’s the idea of action through the square occupied by the black king which is the theme of the problem. So what does White do after 1...c6 or 1...c5? The problem with 1...c6 is that it blocks the line b6-e6, and White replies 2.Qf7, threatening 3.Qxe6#. Previously this could have been met by 2...Kxe5, but now that the rook’s line of action through the black king has been blocked the defence no longer operates. Similarly 1...c5 blocks b4-e7, so that after 2.Nxg6 the defence 2...Kxd7 no longer helps.

Abram Gurvich, 2nd Prize, Shakhmaty 1929 (version)

White to play and win

There’s really only a single line of play, so once you have found the slightly tricky second move it’s just a question of working forward, making threats which keep Black off balance, until the finish becomes visible. Material is roughly level, so in order to win White must exploit the awkward position of the black king.

1.Nb2 (attacking the rook and also threatening 2.Be7+) 1...Re4 (1...Rc7 loses in various ways, the neatest being 2.Rg4 b5 3.Bd2 Nc6 4.Ra4+ bxa4 5.Nc4#) 2.Be3 (the key move, attacking the knight and threatening 3.Bc5+) 2...Nc6 (2...Rxe3 loses to 3.Nc4+) 3.Bc5+ Nb4 4.Nd3 a5 (Black’s moves are all forced) 5.Bxb4+ axb4 (the pin disappears, but the black king is dangerous exposed to attack along the a-file) 6.Rg8 Re6 (there’s no choice, since 6...Ka4 7.Nc5+ and 6...b2 7.Ra8+ Kb3 8.Nc5+ both cost Black his rook; now everything is set up for the study’s finale) 7.Ra8+ Ra6 8.Rxa6+ bxa6

9.Nb2. A comical situation – the black king is stalemated and he is forced to commit suicide by pushing the a-pawn until it takes away the king’s last flight square. 9...a5 10.Ka1 a4 11.Nc4#.

This is a really attractive study with a single very clear line of play. Thankfully it lacks the analytical complexities which often obscure the basic idea in many modern studies.

Part two of John Nunn's solutions to his selection of compositions will follow next week.

The scores of the 39th World Chess Solving Championship may be found here. If you would like to tackle the remaining problems you can find them here (with the solutions given on this page). The Poles deserve a big thank you for organising a splendid event and I am sure everyone is looking forward to Belgrade in 2016.

Finally, I would like to thank global investment managers Winton for sponsoring the British team. Without their support it wouldn’t have been possible to field our top solvers and gain the silver medals in Ostroda.