Takenaka chose the triangled point. He first mentioned the approach move at A but then White could pincer at B or C. On the face of it, he seems to be saying nothing about why he rejected it, but there's an interesting translation subtlety. English students are (or were, in my day) repeatedly advised to eschew the passive tense in writing. It is therefore common for a translator to render the Japanese here (literally "I would be pincered") as "White would pincer." This changes the subject and the emphasis - massively, I think. The passive is also usually considered "adversative" in Japanese. The upshot, anyway, is that Black is implying "I don't want to, or must not, be pincered."

Next, Takenaka mentions B - "one space wider." He concedes this is plausible, but then adds: "It would lead to an ikken-tobi game," with Black jumping to D.

I confess that I am not entirely sure why he seems to be implying that an ikken-tobi game is not to his taste, but there is, I think, an important clue in the word "wide." The Japanese word (hiroi) has almost a technical status and is very common. It could be translated often as, say, "open" but "wide" extensions are an important aspect of open play. In those no-komi days, it could be taken for granted that everyone knew that Black tended to shy away from open/wide play so as to preserve his advantage of first move. I'm certain that applies here, but would be interested to hear opinions on how this relates to ikken tobis.

But Takenaka goes on to explain that he decided his move was superior to B because White will eventually play the shoulder hit at E, and the thickness he will accrue there will make invasion at the top troublesome for Black. I think the interesting aspects are that he is thinking of the reducing move as thickness and that he is expecting the shoulder hit - in other words he is not thinking of this area as Black territory or with any expectation of getting the ikken tobi to build up his framework. On the other hand, he appears not to be thinking of any follow-up moves - he is treating this as an upper-right quadrant only problem (and the course of the game seems to validate that - perhaps we can see this as Black laying down a spider's web, luring White in).

Note also that, while he evidently expected the shoulder hit on the right side, he strongly implied that, had he extended wider on the upper side, he would get the ikken tobi there, i.e. White would not shoulder hit there. Interesting to consider why - the direction of the thickness seems to hold the answer.

I would expect many amateurs to play the triangled stone instead of A, but for reasons such as "Keep away from thickness" or "Else Black could invade." But Katos' reasoning was that A would give Black perfect momentum to jump to B. Momentum (choshi) is a major strategic concept mostly absent from amateur play. Incidentally, neither White's move nor A is strictly an extension (hiraki), but a tsume, often translated as "checking extension." So this term alone tells us a lot about what was going on in White's mind (i.e. he was blocking Black's development, this being the main purpose of a tsume, so going to A and encouraging Black to develop at B must be a no-no).

You will note that Black has adopted a slightly unusual but still standard line of the joseki on the left which emphasises solidity. So that is one factor. Kubomatsu said he chose the triangled point because he intended to continue on the left side as shown in the game - see below. Also, he rejected Black A because that gives White too good a move at B.

But maybe the most interesting thing is the word he used to described his play. It was not an "extension." It was a yose move. Yes the yose (if translated properly as "boundary play") can begin as early as move 15 and in centre field.

This usage is a little unusual, though certainly not rare. Kakoi (surrounding could be used instead). But either way the term gives us an insight into Kubomatsu's thinking in this game - he was going for early territory, hence an early boundary play.

The position after the next few moves will illustrate further what he planned:



Black's play on the left side could also be called yose rather than thickness building. As I've said before, thickness is really thickness only if it can function as thickness, and in this game there was no call for that. In fact this game could be called one long yose sequence - see the final position.


It is possible to argue that Kubomatsu was being wise after the event in using the term yose, but given the plethora of articles (and a famous book: Tengen and New Fuseki) by him, and many other games, in which he emphasised the centre and discussed the problems associated with sealing it off, I think we can safely assume the "Great Amateur" was an AlphaGo trailblazer of the 1930s. He won by 6.

Iwamoto played at the triangled point and commented that this sort of situation of having to decide between this move and a jump to A arises often, but it is never clear which is better. I think it is important to remember that fuseki is very hard even for pros, even in cases that allegedly come up often.

However, there are not too many database examples of this particular upper-board shape. In most cases, Black does indeed play on the middle of the upper side, though not always at the precise triangled point chosen by Iwamoto. But I can find no example of the jump. The same situation obtains even if we change Black's shimari to a small one.

That is not to say, of course, that Black does not give the jump very serious consideration. Assuming a genuine decision is being made, therefore, as in Iwamoto's case, what sort of factors go into the mix? In Iwamoto's case he did not explain directly (nor, unfortunately, did he comment on high or low), but he did make a comment about his previous play which probably indicates one thing that swayed him: he said that the result in the lower right was a little overconcentrated for Black, whereas White was rather thick.

Maeda commented that had Black played the jump to A, he would have responded with White at the triangled point. But Iwamoto said to that that he would just play B, which seems to hint at a little regret on his part. He won anyway, without counting.

I confess to missing the best capture in the lower right - or, more precisely, I was too lazy even to look: White plays S1, not the P1 I on auto-pilot would have done.

If I would play on the top side, I would also play j16. That kind of high and far extension (one further than star point) is one I've tended to play more in recent years. I like that it makes white's checking extension smaller, and being on the 4th line has more effect reducing the influence of white's high shimari (if 3rd line then shoulder hits or caps or knight's moves can develop the centre to left for white later). And s1 on the lower side is easy to see when asked but I too might miss it in a game.

But the first thing I looked at on this board was black's lower left group which I'd assume white attacked at c8 recently. My first feeling would be to see it as a weak group and do something with it: jumping out to f8 is a standard move in handicap games but is rather ponderous (a bit slow but trying to make miai of pincers on left or lower side, but despite the h3 gap white's pretty strong there). So then I would think about g4 to get out and would white answer at h4 (if so pincer at d11 next?) and would that be a good exchange for black (I feel probably, you lose an invasion, but that invasion is unlikely)? j4 is another idea but probably overplay given white's thickness at m4. Black's not going to die if he tenukis, so if black did something like f6 which has no spectacular follow-up I'd worry about white playing a big point on the top side (extend from his shimari and start a double-wing, stop my shimari extending and making double wing), so perhaps the flow of the game is white just played c8 and black cannot afford to make any local answer as it's basically miai with the top: if c8 was the last move and instead white played at k16 (for example) then black would play on the left side (c10 is a local joseki but feels a bit timid, so c13, or something more advanced?).

Mukai said: "There was a strategy behind Black 27 (triangle). If White continues by attaching at the 3-3 point A in the usual way, Black would normally hane inside at B, and then after White C, Black D a furikawari trade would ensue, but in that case Black 27 would be better at E [not explained, but why?]."

He went on: "But the reason I played 27 was that if White did play at the 3-3 point A, then I thought I would try simply playing the hane on the outside at F and making the hanging connection after White B, Black G."

He did not explain why he thought that might be better, but two factors seem to be relevant. One is that Black appeared to have his eye on playing H in the lower left (as happened in the game) rather than the usual I. He said I is bad here because White will attach at H. Also, the open skirt in the upper left will govern Black's assessment of what he can do in the lower left.

White appears to have sussed out Black's thinking and so continued with the attachment at E. This has now become known amongst pros in the last couple of decades, but was a novelty then and remain apparently uncopied until 1996. Fukuda's assessment of it was that it seemed a little heavy. The result of the "joseki" is shown below - more shades of AlphagGo (but White lost here).