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 Post subject: Question on proposed invasion in book problem
Post #1 Posted: Sun Aug 07, 2022 11:19 am 
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I am working through Graded Go Problems For Beginners and came across this problem. The question asks where Black should play. The answer is 1 and it says "Black next aims to invade at the point A."

This seems overly aggressive and somewhat suicidal. Would this invasion be possible if White jumped out in response to 1 or only if white does not answer blacks 1? Would anyone be able to show how this would work or some variations? I have tried playing a couple of variations but it seems that White would be able to kill Blacks invasion.

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 Post subject: Re: Question on proposed invasion in book problem
Post #2 Posted: Sun Aug 07, 2022 12:13 pm 
Gosei
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Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . 1 . O . . a . O X X . . . |
$$ | . . . , . . . . . , . . O . O , X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


When the book says that "Black aims to invade at A", it means that "if White doesn't respond to :b1: then Black can consider to invade at A".

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 Post subject: Re: Question on proposed invasion in book problem
Post #3 Posted: Sun Aug 07, 2022 12:54 pm 
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I am going to try to explain in a different way.

a) You need to seek out moves that have more than one purpose. In this case, the solution given by the book gains territory AND threatens the white group below with invasion. I'll come back to this, but it is NOT "suicide" << if white fails to make a defensive move in response to back "1" >> So black made a move that gained something and white has to respond not to lose what had appeared to be white territory. That means black gets another turn to gain something.

b) That formation of white stones is one alternative in a common joseki. You'll see it used in a lot of games. It has the potential of gaining more than the other (safer, more solid alternative) BUT it has a weakness. If black does have a stone at "1"it CAN be invaded if you know how. The white stones will be safe, but the territory lost. You'll have to look for examples of how this is done in books covering just after joseki.

c) So ..... you can't JUST use problem books because you will every now and then run into problems like this one where getting to the right answer depends on other knowledge. In this case, that the white formation below was not safe from invasion.


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 Post subject: Re: Question on proposed invasion in book problem
Post #4 Posted: Sun Aug 07, 2022 1:32 pm 
Gosei
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More details here: https://senseis.xmp.net/?34PointHighApp ... Connection


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 Post subject: Re: Question on proposed invasion in book problem
Post #5 Posted: Fri Aug 12, 2022 6:42 pm 
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jlt wrote:

Just in case the variations are too complicated, here's a simpler way of looking at it:

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . b . . . a . . . . . |
$$ | . . . X . . B . O . . 1 . O X X . . . |
$$ | . . . , . . . . . , . . O . O , X . . |
$$ | . . X . . . . . . . c . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


After :b1:, black has three directions to run towards: a, b or c. (Maybe c isn't exactly the right point, but something in that general area should work, depending on white's previous move.) So on general principles, you can feel pretty confident that :b1: won't be suicidal.

Here are two things that shouldn't happen, because they're too good for black:

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . 7 4 3 . . . . . |
$$ | . . . X . . X . O . . 1 5 O X X . . . |
$$ | . . . , . . . . . , . 2 O 6 O , X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


In the above diagram, :w4: tries to disconnect black but fails.

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 4 3 . . 2 . . . . . . |
$$ | . . . X . . X . O 5 . 1 . O X X . . . |
$$ | . . . , . . . . 0 6 7 . O . O , X . . |
$$ | . . X . . . . . . 9 8 a . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


The next move would be black 'a'. Here, you might think that black is in trouble because :b1: is weak. But white is also split into two weak groups, so it's a fair fight, or perhaps slightly better for black. The move at :w4: was probably too violent (depending on what the rest of the board looks like), and should have been somewhere in the region of :b7: instead (in which case black would play at :w4: and connect to the stones on the left).

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 Post subject: Re: Question on proposed invasion in book problem
Post #6 Posted: Sat Aug 13, 2022 11:35 am 
Judan

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The fact that black's invasion is not suicidal is a clue why we start in the corners: the corners are a much easier place to make secure territory and eyes than on the sides (which themselves are easier than the centre).

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 Post subject: Re: Question on proposed invasion in book problem
Post #7 Posted: Sat Aug 13, 2022 12:38 pm 
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Uberdude wrote:
The fact that black's invasion is not suicidal is a clue why we start in the corners: the corners are a much easier place to make secure territory and eyes than on the sides (which themselves are easier than the centre).


I agree with your conclusion, but not necessarily because the invasion isn't suicidal. Maybe the simplest corner example to think of is the 3-3 invasion, which also is not suicidal, albeit in the corner.

Despite this, the corner is indeed more "secure" and easier to deal with than the sides in many cases.

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 Post subject: Re: Question on proposed invasion in book problem
Post #8 Posted: Sun Aug 21, 2022 11:57 am 
Judan

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minkzilla wrote:
Would this invasion be possible if White jumped out in response to 1 or only if white does not answer blacks 1? Would anyone be able to show how this would work or some variations? I have tried playing a couple of variations but it seems that White would be able to kill Blacks invasion.


The invasion is fairly easy (once you know how) if white doesn't answer, others posted some variations for that. But even if white does answer with a jump, black still has some invasions possibilities, here is a textbook sequence (for later):

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 8 7 . . 6 . . . . . . |
$$ | . . . X . . 1 . O . . 5 . O X X . . . |
$$ | . . . , . . . . 4 3 . . O . O , X . . |
$$ | . . X . . . . . 2 . . 9 . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

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