Hi,

If your opponent has a territory, and you have the opponent surrounded, then who's territory is it?
For example:

Black (X) and White (O) surround each other. Does this territory belong to black or to white, or does it need to be played out to decide who's territory it belongs to?

If it needs to be fought out, then why do opponents not always invade each other's territories to try and create eyes all the time. Why are territories ever left without a fight once they are surrounded. I have seen many games where I think I would continue fighting, but more experienced players don't?

Thanks
Regards
Craig.

I'm noob myself too, but i think it's simply becasue the better players had been in this situation many times before and/or can clearly see outcome of such attempt as an failure. I think for You it's just best to try it and see why it does or doesn't work.

_________________
My go blog - in czech: http://go-blogisek.posterous.com/

Craig, all good questions. 1. If the invader ( in your example) jumps in and kills B, then it becomes all W's territory.
2(a) If B can kill the invading W stones, AND B gets a life shape, then B keeps the territory as B's.
2(b) Even if B can kill the invading W stones, if B ends up with a dead shape, then it reverts to case (1) above.
3. If B and W end up as seki, it's more complicated -- depends on the seki shape.More experienced playes will be able to tell whether the invader can live or die.
This is where lots and lots of Life-and-Death exercises and reading skills and experience enter the picture.Because some invasions are good and some are bad (for the invader). If the invasion is good for the invader, the invader invades. If not, then no.Because they already know the (likely) outcome of any invasions. At your level, if you are not sure, jump in and find out -- it's the best way for you right now: experiment, and find out for yourself.

First of all, you can see how to make a diagram here: viewtopic.php?p=1693&f=5#p1693

This makes it a bit easier to see what you mean

Click Here To Show Diagram Code

[go]$$
$$--------------
$$|O O O O . . . . . .
$$|X X X O O O . . . .
$$|. . X X X O O . . .
$$|. . . . X X O . . .
$$|. . . . X X O . . .
$$|. . . . X X O . . .
$$|. . . . X X O . . .
$$|X X X X X O O . . .
$$|O O O O O O . . . .
$$|. . . . . . . . . .
$$|. . . . . . . . . .
$$|[/go]

Black is the one surrounding empty territory, so it belongs to black unless white can either:
a) create a living group in the empty area or
b) kill the black stones.

For white to create a living group, i.e., one with two eyes, inside that enclosed space is highly improbable because there is just not much room for him to do so and it should be fairly easy for black to prevent white from getting two eyes.

However, it is possible to imagine a situation in which white invades, black tries to kill him, but in the process removes too many of his own liberties resulting in either his death or a seki (where putting one's opponent in atari would put oneself in atari).

If white thinks he might have a chance at killing or getting a seki (in which neither player would get points in the enclosed area) he is welcome to try, and indeed a beginner can learn a lot by trying. More experienced players however recognize from their experience and their ability to read out a position whether an invasion is futile, so they don't bother.

Here, if white can prevent black from forming two eyes, he might have a shot. If you can't read that it's impossible, bombs away! Likewise for black - if he thinks white has a chance, he might prevent it by tossing in another stone for protection - but that makes his territory one point smaller, and if the invasion was doomed from the start and he loses the game by that one point, that will have been a big mistake!

P.S. Welcome to the forum!

_________________
Patience, grasshopper.

When, as in your example, one player has surrounded points in a (currently) single eye, and the opponent has surrounded that player's group, and the opponent's surrounding stones are alive, how do you know whether that player's group is alive? That is an empirical question.

In your example the player's group is solidly connected, without a cutting point. Such groups have been extensively studied. The question is whether the opponent has an effective play inside the player's eye. Such a play is called an inside play, or nakade. (See http://senseis.xmp.net/?Nakade .) When there is one cutting point or more, whole books have been written on the subject.

If there is no cutting point and the eye has fewer than two points, the group is dead. If the eye has three points, the group is unsettled. The player with the move can live or kill. One rule of thumb is that if the eye has more than seven points, it is alive (with some exceptions). That does not mean that the opponent to move cannot make a seki. (Your example has many more than seven points in the eye, and Black is alive.)

As you are a beginner, I would suggest that you play by area scoring ( See http://senseis.xmp.net/?AreaScoring .), because then, after the dame stage, it does no harm to play inside your opponent's presumed territory.

Good luck!

Edit: P. S. A good study tool for these and other positions is Thomas Wolf's Go Tools ( http://lie.math.brocku.ca/GoTools/index.php .)

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

The game isn't over until you're certain, so play some moves in there and make black prove the area is his.

Conversely, if you are black, and you aren't sure you can kill anything white plays in there, add moves until you are sure. If your opponent is passing, he's saying he doesn't think he can live in there, and of course in that case you should agree with his cowardice and also pass.

_________________
That which can be destroyed by the truth should be.
--
My (sadly neglected, but not forgotten) project: http://dailyjoseki.com

People don't invade every opponent "terrritory" because the opponent might not respond so if the invasion doesn't succeed the invader loses points. When you are a beginner no one will object if you just invade to see what will happen, especially if you don't know yourself whether or not the invasion can succeed. But if you play invasions that obviously can't succeed some people would consider such invasions to be rude behavior.

Just to catalog some of the reasons people have mentioned for why *not* to invade:

1. If you're sure the invasion will die, invading would prolong the game unnecessarily.
2. If you're sure the invasion will die, you might not want your opponent to think that you didn't know that.
3. If you're sure that even if your opponent ignores your move and lets you play a second stone, the invasion will still die, invading just causes you to lose a point.
4. If you invade and the invasion dies, you'll have strengthened your opponent and lost your ability to reduce his territory from the outside.
5. If you're sure that the invasion will die, but that you opponent can't ignore your move, you want to save the invasion for a ko.

Note that reason -4- replies in reverse, too. Sometimes you don't want to wall off your opponent from the outside because that ruins your chances to invade and live inside.

This is the converse of your question, but: If you are behind and you will lose if you don't invade, you should close your eyes and invade. If there is zero chance, you can resign (but at your level, I'd think twice before deciding you don't have a chance).

When you want to invade, you have to keep in mind that you have to make a living group within your opponent's territory. The smallest living groups are shown on this diagram:

Click Here To Show Diagram Code

[go]$$
$$-------------------
$$|X . X . . . . X . X X . . . . . X X .|
$$|. X X . . . . X X . X . . . . . X . X|
$$|X X . . . . . . X X . . . . . . . X X|
$$|. . . . . . . . . . . . . . . . . . .|
$$|. . . . . . . . . . . . . . . . . . .|
$$|. . . . . . X X . . . . . X X . . . .|
$$|. . . . . . X . X X . . X X . X . . .|
$$|X X . . . . X X . X . . X . X X . . .|
$$|. X . . . . . . X X . . . X X . . . .|
$$|X X . . . . . . . . . . . . . . . . .|
$$|. X . . . . . . . . . . . . . . . . .|
$$|X X . . . . . . . . . . . . . . . . .|
$$|. . . . . . . . . . . . . . X X . . .|
$$|. . . . . . . X X X . . . . X . X . .|
$$|. . . . . . X X . X . . . . X X X . .|
$$|. . . . . . X . X . . . . . X . X . .|
$$|. . . . . . X X . . . . . . X X . . .|
$$|X X X X . . . . . . . . . . . . . . .|
$$|. X . X . . . . . . . . . . . . . . .|
$$ ---------------------------------------

$$|[/go]

In the corner you need at least six stones to live, at the edge eight and in the middle of the board you need at least ten stones.

Since you and your opponent set stones alternatively, you also have to keep in mind that he wants to prevent you from making two eyes for your invading group. That means that some weaknesses must exist in the phalanx of your opponent's surrounding stones. You have to exploit theses weaknesses by threatening something, e.g. atari some of his stones, connect to outside groups, cut off some of his stone in order to capture etc. This is a complex matter (for advanced players) where you would have to read out the situation deeply. There are tesuji for that purpose, so studying them would probably help you with that. As you are a beginner, I'd recommend what some people have already recommended: try it out yourself what works and what not.

Hi Everyone,

Thanks very much for all the great responses.
I understand the issues much better now, and realise that understanding whether or not white can invade and remain alive underpins everything.

I will continue to learn.

Cheers
Jim.

Simple question: Why on't I put a white stone into the black territory, so that it decreases from 18 to 17? If black wants to catch me, he has to put 4 stones around it and therefore loses four points. There must be something wrong with my thoughts, right?
Yes, I'm a beginner

Click Here To Show Diagram Code

[go]$$
$$--------------
$$|O O O O . . . . . .
$$|X X X O O O . . . .
$$|. . X X X O O . . .
$$|. . . . X X O . . .
$$|. O . . X X O . . .
$$|. . . . X X O . . .
$$|. . . . X X O . . .
$$|X X X X X O O . . .
$$|O O O O O O . . . .
$$|. . . . . . . . . .
$$|. . . . . . . . . .
$$|[/go]

This one stone is dead unless you manage to let him live.
It does not reduce your opponents points.

It depends on a ruleset a bit (with chinese rules you don't lose points by playing inside your own territory, so this aspect is easier to grasp for beginners). Here black has to be careful not to end in seki, but generally if white plays in his territory, black can say (to himself) "no, you cannot kill me or make seki" and pass. If white continues, he can ignore until it threatens his life and then capture white. Notice that even then he doesn't need to physically capture every white stone, if they don't have chance to live / kill black. If white doesn't agree with him, they can play the situation out.

OK, but if I wouldn't agree as white, I mean if I insist on "you cannot kill me" (even if I know better) we have to play it out. Then black will kill white, but to achieve this, he needs to play inside his territory. And with japanese rules, he loses points then! Is that right?

Black will also capture a number of white stones similar to the number of black stones he had to play. The score will remain the same.

http://senseis.xmp.net/?JapaneseRules :
Resolving disputes about life and death or protective plays depends upon hypothetical play with special ko rules.
hypothetical play = you play it out and then go back to original situation.

This worries beginners a lot. I think it helps to understand the original rules of the game and what the "Japanese" rules (i.e. the rules developed during the Tang) and the "Chinese" rules (i.e., the rules developed during the Qing) are trying to accomplish.

Originally the goal of go was to get more stones of your color on the final board. The board was completely filled, except (almost certainly) for the two eye spaces required for each group to live, and the stones of each color were counted up. Of course, for this stone-filling game to work, you need to have a capture rule; otherwise, as the players alternate placing tiles, the first mover will always win by one. But once you have a capture rule, the goal of the game becomes to have the stones you place now protect spaces that your opponent can't play on without being captured (or risking capture). That way you can fill in as many of the open, unprotected spaces as you can, and then still have more protected spaces inside your group to fill in at the end.

To beginners and GnuGo, this way of playing was probably very reassuring. To people who have been playing for a while, though, it is both boring and a bit inelegant. Once all of the spaces than can be protected from the opponent's stones are protected, then you split the remaining points that can't be protected evenly down the middle (the person who takes the first worthless middle space might sometimes get one more point here than the person who takes the second worthless space); then you have to completely fill in your own territory with your own stones. Boring, right? What's going to happen is a foregone conclusion.

So sometime around the Tang period, go players introduced an innovation. They just stopped filling in the almost-worthless points in the middle that didn't protect any extra spaces, and didn't count them for either side; and they stopped filling in the protected spaces, and just counted them for the side that surrounded them. And, making, things even easier, instead of having your stones that are still on the board count towards your score, they had your stones that were captured or doomed to capture count against your score. It comes out to the same thing (with one small difference), and allows you to dump the captures inside your own group to easily calculate the score at the end. --- As you have already guessed by now, this is the form in which Go went to Japan and thence to the West. We call the protected areas that used to get filled in at the end of the game "territory" and the least-valuable points which didn't affect territory or the life of groups "dame".

But you can see that this change wasn't really intended to affect anything other than the boring, inelegant stone filling stage at the end of the game. People were not supposed to have disputes about which stones were alive and dead once there were no more moves left that effect territory/captures. Indeed, experienced players know that if the life and death of the stones was in question, the player who claims they are alive would be desperate to keep playing, so as to give them two distinct eyes or capture enemy stones. With very few exceptions, when a player is claiming that his opponent has to make more moves to capture, but he refuses to play any more stones on the board himself, he is acting in bad faith.

However, there are a few exceptions that are genuinely confusing even to experienced beginners, and in the Japanese system they came up with a special set of rules to resolve them.

The Chinese rules came later. They're very similar to the Japanese rules, except that they do fill in the dame and do not keep track of captures. So, like the Japanese rules, the Chinese rules call for counting empty territory that was originally filled in, but instead of having captures count against territory, they stones on the board added to territory. It's the same thing, remember - each player has usually played the same number of stones, +/-1, so stones on the board plus dead stones for black equals on the board plus dead for white. Because the stones on the board count again, you get an advantage from filling in all the worthless spaces in the middle of the board. What's true under Japanese rules is true under Chinese: if your opponent insists that you need to captures his stones at the end and isn't willing to play more stones on the board himself, he's probably acting in bad faith. But because under Chinese it doesn't matter anyway, you can just keep playing and adding more stones inside your own territory to make the opponent happy.

Summary: The original rules involved filling in the entire board. Everyone agrees that's boring. We now have two different rulesets that implement the idea of not filling in the whole board. The result should be the same (+/- 1 point) in almost every single game of go. A good move in Japanese rules is equally good under Chinese, and vice versa. Their only disagreement is what to do once all the territory is settled. In Japanese rules you stop, and resolve disputes about which groups are dead by not being an cad. (Hehe, cad gets filtered to cad.) In Chinese rules you split the dame and resolve disputes by plunking stones down on the board until you've filled in your entire territory, if that's what it takes to convince you're opponent to be a good sport.

Just a random point: I'm not sure about the timing of the Chinese and Japanese rules. I guess you can claim that Chinese rules as we know it come later, but it (area scoring) really is the fundamental counting method (with group tax) much earlier than the Japanese rules (territory scoring). In other words, if there were ever a time when people played until the board was filled, it ended very early.

I think territory were more used as a quick count alternative to area scoring and was passed to Japan where it became more popular than area scoring.

Of course, I'm not an expert (or even reasonably knowledgeable) on this, but it seems weird to claim that Chinese rules came after Japanese rules.