Life In 19x19

In the general case,what should you do when someone invades your territory?Try to take his stones or try to isolate him? I'm talking about move 101 and move 119 in this game.

Vally79. You did the right thing for 101.
The invasion underneath the corner starpoint(3-3) is a pretty reliable one. Although if your R13 stone was one line closer it could be a ko for life.
The kind of annoying thing about Go is that questions like what to do in response to an invasion kind of have to be answered: "It depends."
Some things to consider.
Assuming White gets a play around L10 to seal black out of his area, I count white being ahead by a fair bit. So sealing black into the corner and making it that much harder to invade the rest of your area is good.
However, if you would lose if black lives then you need to go for the kill even if it is unlikely.

You didn't respond to K17(119) very well though.(You need to kill this by the way and it should be doable)

Click Here To Show Diagram Code

[go]$$Wc perhaps start this way?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . 3 . . . . O . . . |
$$ | . . . O . . . 1 . B . . 2 . . O . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . O . O . . |
$$ | . . . . . . . . . . . . . . . O . O O |
$$ | . . . . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . O . . . . . . . . . . . . |
$$ | . . . , . . . O . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

There are other options but, your right side wall he just gave you is strongest so shove him that way then, you can steal the base with L18. At which point with no eyes and all your stones in the middle Blacks basically dead. In theory, I have a lot of games where the other guy is basically dead and lives any way.
Your main problem was attaching, it makes Black stronger then he needs to be. A good attacking guideline is don't touch if you don't have to. The trick is of course knowing when you have too. Conversely attach away if your the weak party and trying to live

So IMHO these two invasions are pretty illustrative. The first one it was fine to seal black in and take an amazing amount of ingluence. But the second one was something that needed to die.

Thanks, Twitchy Go! By the way,could the large taking of stones in the center have been avoided in some way?What's the wrong move leading to that?

In Go contact plays are not very good attacking moves, since it's easy for the defender to increase their group's liberties. Keeping a short distance is actually a stronger way to play, since it leaves room for making strong shape. You responded well to black's invasion at move 101, making strong wall facing the outside. 119 invasion is more difficult to kill, since the space is so open. You could protect large areas like this one by playing there first before opponent invades. If the invasion happens, before trying to kill, block direction(s) of development for the invasion stone.

In general? Cut, Connect, Surround.

Not in that order.

Before you go trying to kill an invasion check that your own groups are okay. Have your groups been cut into one or two weak groups? If there are any weak groups how easily can they connect to each other or to other stones.

When you decide you are safe enough to kill then you can try to surround the group to make sure it doesn't get any deeper into your territory, and also force it to make eyes and live.

If you can't easily surround it try to cut off it's path to other stones.

Click Here To Show Diagram Code

[go]$$Wc perhaps start this way?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . O . . . . . B W . . . . O . . . |
$$ | . . . , . . . . . B . . . . . O . . . |
$$ | . . . O . . . . . . . . . . O . O . . |
$$ | . . . . . . . . . . . . . . . O . O O |
$$ | . . . . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . O . . . a . . . . . . . . |
$$ | . . . , . . . O O , . . . . . , O . . |
$$ | . . . . . . . X O X . . . . . O . . . |
$$ | . . . . . . . X X . X X O O O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

the board ended up looking something like this.

Black has only one way to connect out. if at any point between W120 and W150 white had played the at a
Black would have had to live inside white's territory with no hope of connecting out.


edit:

I suppose it might fall into the surrounding category. But minimize eye space is another way to think of your moves.

Squeeze your opponents stones as flat as possible so they don't have as much room for eyes.

Vally79 wrote:Thanks, Twitchy Go! By the way,could the large taking of stones in the center have been avoided in some way?What's the wrong move leading to that?

The wrong move leading to the large taking of stones was every move 120 on. That sounds rougher then it is. The problem is your fundamental understanding of attacking, not your tactical sense. Since you choose plays under a faulty premise it is hard to figure out good moves! As Toge and Unusedname have been saying,[paraphrasing here] The best way to apply pressure is from a distance, getting to where your opponent needs to be before he does. i.e. Playing a move that cuts his path off to the center, playing a move he would like to play in order to make a base, playing on a shape point that will wreck eye shape. Touching your opponents stones will generally give you a whole lot of cutting points to deal with and you'll likely lose some stones and let him live.

And although in this case I still think you need to kill this invasion to win. It is often times better to allow them to live on your terms. By forcing them to live with just a few points, you make a very powerful outside position.

Dealing with an invasion boils down to a more fundamental issue. How to attack severely. Since it is an invasion you should be strong in the area already and be able to get a good result even if your opponent lives with a few points. Attacking as an abstract concept boils down to direction of play(but everything sort of does). You don't have the goal of killing in mind when attacking but rather how to profit best.

Click Here To Show Diagram Code

[go]$$c direct invasion of the low chinese
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . B . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X X . |
$$ | . . . . . . . . . . . . . . . . B O . |
$$ | . . . . . . . . . . . . a . . X . O . |
$$ | . . . . . . . . . . . . . . 8 O 6 . . |
$$ | . . . . . . . . . . . . . 7 9 0 . . . |
$$ | . . . . . . . . . . . . . . . W . . . |
$$ | . . . O . . . . . , . . . 1 . , 4 . . |
$$ | . . . . . . . . . . . . . . . B 2 . . |
$$ | . . . . . . . . . . . . . . . . 3 5 . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Here is an example . Black set up a low chinese and white jumps in right away at the marked stone(which you don't want to do by the way). I've laid out a standard sequence from this invasion. This is an invasion of blacks framework, but he is not strong enough to kill. So how does he handle it.
Drawing an imaginary line to the marked black stone at R9 we see that black has put white behind his territory line(sector line) and is threatening to surround. He also builds up the bottom a little in doing this.
White attaches to start making a base.
Black plays here to make white struggle more for his base. If white got to take this point he would be very happy.
saves a base is starting
Black opens up a monkey jump reduction later, effectively removing white base again. This means white still has to struggle.
white makes a 2 space extension and has a base again.
Threatens to seal white in, effectively giving black a wall that spans half the board. This would be a disaster for white. [Side note: don't get sealed in during your games, it's worth WAY more then you think.]
This lets white get out while making shape.
Black pokes out the shape and white defends.
Black peeps at Q8: again threatening to seal white in.
White forces an exchange to finish his base. Black doesn't cut because solidly sealing white out of his space is better. And white protects the peep.
White gets six points(after the reduction) and is out in the center. But if black later gets in a move around a white should go back and make sure he lives.

In summary. Black gets to nicely develop the bottom and the top right while white struggles to make sure his invasion is safe. This is the mindset you want to have with invasions. Although killing them is nice too.

Addendum:
Preempting EdLee a bit here
Broken Shape is Bad!

Click Here To Show Diagram Code

[go]$$c broken shape
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . W X X W . . . . . . . . |
$$ | . . . , . . . . . X X . . . . , . . . |
$$ | . . . . . . . . . W . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black has one group to worry about, while if your planning on killing you have three. This puts you at a disadvantage in fighting. In general when attacking stay as solid(connected) as possible and look for good opportunities to cut the other guy.

116: At T18
118: At K17 or so

jts wrote:116: At T18
118: At K17 or so

Yeah...
I feel silly about missing that.

By the way, this is a fun trick:

Click Here To Show Diagram Code

[go]$$Bc Cut or no cut?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O X XX |
$$ | . . . O . . . . . W . . . . . O X . . |
$$ | . . . , . . . . . , . . . . . O X X . |
$$ | . . . O . . . . . . . . . . 2 1 O X X |
$$ | . . . . . . . . . . . . . . . 4 3 O O |
$$ | . . . . O . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code

[go]$$Bc Cut or no cut?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O X XX |
$$ | . . . O . . . . . W . . . . . O X . . |
$$ | . . . , . . . . . , . . . . . O X X . |
$$ | . . . O . . . . . . . . . . 2 1 O X X |
$$ | . . . . . . . . . . . . . . . 3 b O O |
$$ | . . . . O . . . . . . . . . a . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

I'm not sure whether A or B is better for in the second diagram. But the point is, you don't really need to save that stone.

Vally79 wrote:In the general case,what should you do when someone invades your territory?

1. Make a positional judgement.

2. Imagine every possible tactical and strategic development, such as playing elsewhere forcing your opponent to play elsewhere, playing elsewhere and starting an exchange, killing, surrounding, blocking particular directions, getting territory compensation, getting influence compensation or getting aji compensation. If (still hypothetically) you attack, usually do so in sente as long as possible and concentrate on important strings and valuable regions rather than non-essential strings and neutral regions.

3. Choose the best development for the positional judgement.

Actually neither 101 nor 119 invaded your "territory", strictly speaking.
Both moves point out weaknesses in your formation. E.g. the 3*3-point is the main weakness of the 4*4 point.
In my opinion the real question is when to defend your formation, so that it becomes territory? In this game you could have used your move 86 to defend the top right right corner (P17 maybe). 119 might look slightly overplay-ish but altough it should be hard to live, it is also not easy to kill. You still could have defended on move 111 (K16 maybe).

Regarding your question: When you can kill cleanly, kill, when you can't, let your opponent live small (surround him). If both fail, you should have definitely defended beforehand.

I’m too weak a player to be of real help, but a few things immediately came to my mind when I read the headline:

- If my opponent successfully invades “my” territory, then it was not yet my territory in the first place.

- And I think I read somewhere here that the opponent’s stones don’t invade, they immigrate because they felt invited by the open land. Something like that.


Greetings, Tom

Twitchy Go wrote:

jts wrote:116: At T18
118: At K17 or so

Yeah...
I feel silly about missing that.

Or even better:

110/112/114/116/118: L9

Sealing the centre is bigger than killing the corner (which after t15 is a ko to kill with best play from both sides: http://senseis.xmp.net/?JGroup#toc4). It is easy to follow your opponent around the board, even for reviewers .

Vally79, when I looked at the game I didn't see your rank and at the top right up until 110 you could have been a sdk player. Sealing black in so he lives in gote is good. In fact black played badly there so you could consider 106 at s15 to give black a dead L group in the corner and let him run out but that is a risky way to play as if you fail to kill he wrecks your territory. But then at the top side you played pretty much the exact opposite of how to attack/kill a group. Count liberties. It seems you decided the way to kill the invade was to capture it. But each move you play takes away 1 black liberty, whilst each move black plays can add 2 or 3 liberties to his group. So you are destined to fail. In fact some of your moves were worse than passing as you just created a weak stone with few liberties stuck against a strong black wall! Attacking tanks with tennis balls is a nice way I've heard this described. Instead you should fall back and attack from a distance so your stones have plenty of liberties and kill black not by capturing him, but by reducing his eyespace to stop him making 2 eyes.

Vally79 wrote:In the general case,what should you do when someone invades your territory?

There is no general case. If it is indeed your territory, then by definition you can kill him so doing that is probably a good idea, though sometimes it's better to let them live even if you can kill if you can get more in return (for example good thickness, or lots of profit from chasing their weak group around and torturing it). More likely they invade your territorial framework.

Uberdude, there is the general case, but there is no single low level decision rule for it. All that can be said in general is on a high level. Maybe one can break it down to an intermediate level, by listing all major types of intermediate level cases.

'Territory' exists with different meanings from 'safe' to 'influence sphere'. Apparently, the OP could have better said something like 'region with greater territory potential for the player currently having the greater influence there', i.e., 'moyo' or 'territorial framework'.

Even with the heavy mistakes pointed out by others, it seems to me that White was winning until moves 220 & 222.