The positions are presented twice, one without commentary if you would like to attempt 10 minutes thought on them, and once with a comment cherry-picked from Simon's much more detailed discussion.
I have also added two famous examples of master's thinking.
- 1 - W to move: assume in haste, repent at leisure!
- 2 - B to move: analyse your way to success
- 2/78 - B to move: what is the point at issue?
- 6/78 - W to move: candidate moves?
- 7/78 - W to move: begin at the end
- 10/78 - W to move: playing by analogy
- deG - W to move: what makes a difference?
- LCM - W to move: masters at fault?
[Comment from DR: I might add, that a misjudgement of this sort might lead to much fruitless searching for a winning line if you think you are better. Blumenfeld used to advise trying to look again with a fresh eye at a position to see if you haven't overlooked some simple tactical point, but no less important to make sure you don't overlook some important positional point. I have known players ignore really key features of a position (a Pawn majority, and open file) because they thought they knew what the position was 'about'. Positions in books are selexcted to be 'about' one clear theme. Positions in most games are usually more complex!]
[Comment from DR: This belief is rather widespread. de Groot's research certainly seemed to argue more for the importance of judgement than calculation, but there has been a lot of work since which shows the importance of seeing ahead.]
"JN thought almost exclusively in terms of concrete variations, whereas GJ went to the opposite extreme... RW and SJ also gave very few concrete variations, and this may be more a question of style than strength...
"IC... seemed to have the best-organised thought processes (...) It is not clear, however, whether this logical approach is necessarily all that effective, for it could be argued that if IC had adopted the RW approach of looking at moves twice he might have spotted 1. P-K4 B-N5 2. P-Q5 N-Q5! which seems good for Black" -- Webb
[Comment from DR: This position illustrates for me quite nicely Kotov's notion of 'candidate moves': Korchnoi's actual choice wasn't even considered by the panellists. Korchnoi may even have reviewed, and rejected, other moves that were not considered by them.
Kotov expands his approach to analysis by saying once the list of candidate moves is drawn up, each branch should be considered once and once only. IC has clearly read and believed, and this player may be more efficient because of it, but at least while we are improving this may be at the cost of accuracy. de Groot used to describe an approach of 'progressive deepening', and this may not just a more common approach but a more appropriate one for positions which are not highly tactical.]
[Comment from DR: Howard Staunton complained that only the 'magnates' of the game were really skilled at endgame play, and this remains true!
"JM  's idea of meeting 1. P-B5 with ...PxP and ...P-K5 (was) difficult to spot, because ...PxP is an abnormal way of meeting the thrust P-B5. This also applied to RY and RN , who didn't consider ...PxP because it would have looked anti-positional to them. To AP [ungraded player], however, ...PxP was the obvious reply...
[Comment from DR: I like this observation. It may be that stronger players actually consider more 'stupid' moves than wekaer ones - dismissing most of them, but not ruling them out without a glance! It may be that this is the only possible explanation for, say, some of Tal's moves...]
All the GMs except Flohr quickly found the win with 1. Bxd5 (1...exd5 2. Qf3 Qd8 3. Rfe1 Kg7 4. Ng4 Nxg4 5. Bxe7). They also analysed other forcing continuations like 1. Nxc6, which Alekhin considered just as strong and which Flohr actually preferred.
Hardly any of the other players suspected there was a forcing solution (even after 15-20 minutes, much longer than the GMs. For the most part, they opted for safe positional moves like 1. Rfe1 or 1. Bh6; nothing alerted their antennae to a concrete solution.
Every solver thought: White has an isolated d-pawn, so endgame problems, so attack now. But only the GMs chased it down to a line 4/5 moves deep. The lesser masters seemed unable to overcome two barriers to seeing the tactic: the safe appearance of the Black position, and the anti-positional appearance of 1.Bxd5.
"It is by no means easy to detect these chance factors which are not based on obvious strategic factors", conclude Pfleger and Treppner, rather gloomily.
Oh, Flohr's idea? Looking for something even better than Bxd5, he hatched 1.Nxc6 bxc6 2.Bxd5 cxd5 3.Bxf6 Bxf6 4.Nd7, winning the exchange... but it is only the ghost of the knight that goes to e7!
It looks anti-positional to gove up the Bishop, but Breyer claims an advantage in all lines:
17...Bxf6 18. Bxd5 exd5 19. Ng4 Bg5! (19...Bd8 20. Qf5) 20. f4 exf4 21. Qf5 Bc7 (else 22. Qxd5 a6 23. a4) 22. Nxd5 Kh8 23. Nxh6 gxh6 24. Nf6 Kg7 25. Nh5+ with mate in two.
I have seen this analysis "busted", and I don't feel qualified to judge: but if Lasker didn't overlook something important, then Breyer did!