Order of play - temptation

5-4 joseki...  

This is the starting position. A variation of a 5-4 joseki, with White playing tenuki.

Correct style  

Now is an interesting move. Normally the correct style is to play atari before connecting, however....

The usual continuation  

So why not play in the first place (followed by in the previous diagram)? Because the correct style is to not help your opponent in any way.

A mistake  

This is the sequence Black is hoping for is (ko lock).

White is completely blocked off from the center. This is what I mean by hoping for the opponent's mistakes. Black didn't overplay but the order of moves leaves more scope for White to make a mistake.

5-4 joseki follow-up  

here is in fact the common way to react to .

Another explanation?  

Andre Engels: In which way do they back up this theory? If this is the actual reason, I would expect professionals to play both sequences, since their also professional opponents would never make such a fundamental error in a well-known position.

If Black actually uses only the joseki move order in professional games, I would think that there has to be another reason. My guess would be that the reason is that it has to do with the (very small) possibility that White would answer at here. Black has two answers here: and Black a - White b - Black c. If Black does choose , leaving the Black a - White b exchange unplayed is a plus. Of course this is only a variation of a move () that is played rarely or never, but I guess that's still at least as often as in the 'mistake' diagram is correct, so nothing is lost in being prepared for it.

Charles: The total number of examples Gobase+GoGod is only six (and in one Black makes a hanging connection not a solid connection) so too small a sample.^[1] It's always the same order, though.

Also I wonder about the diagram.

Bamboo joint  

I'd certainly expect and here from Black. Now White needs to spend time living in the corner.

Example  

Here it seems natural for Black to fight back with when White plays (kake). Black has everything to gain by expanding the lower left by fighting.

The atari played  

In this case White does play atari before the connection .

Variation - good for Black?  

It is logical to assume here that the reason is that up to in this variation is interesting for Black, when is played immediately. The stone does look well-placed now, and perhaps White loses control over the lower side.

The atari played - continuation  

This followed, and Black's strategy adds up to a reasonable balanced game. White has two weakish groups, the one on the lower side not really being weak now since White a threatens the corner. Black has a single weak group only.

Variation  

Also mentioned: looks like a vital point of shape, perhaps; but if Black plays there directly before extending at , then leave a and b as miai and Black's plan is in tatters. (Well, Black might have to push from behind, which isn't what purists do.)

Charles Matthews