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| When to defend against the 3-3 Invasion? http://www.lifein19x19.com/viewtopic.php?f=11&t=4611 |
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| Author: | Ortho [ Tue Sep 06, 2011 1:52 pm ] |
| Post subject: | When to defend against the 3-3 Invasion? |
As a 16kyu, I obviously play a lot of handicap games, and I also open on the 4-4 points as white. Sensei's library says that the best time for white to invade the 3-3 point is 1 move before black would defend against it, but I can't seem to figure out when black should defend against it! I know how to defend against it, I just don't know how big it is and when I should take a move out and do it. Most of my opponents invade the 3-3 too early, but I have had a couple of games where we were deep into the endgame and the I had the 3-3 invaded. Surely I should be defending against it before I start playing hane-block-connect on the first line. Is it about the same size as a monkey jump? If this question is too general I can try to post some positions. |
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| Author: | HermanHiddema [ Tue Sep 06, 2011 2:14 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
You should defend against the 3-3 invasion one move before your opponent would invade.  3-3 is not an endgame move, so it cannot be compared with the monkey jump. If an opponent invades in the endgame, it is probably unreasonable. If it isn't, one of you should have played it long before the endgame. So really, there is no easy answer. You'll just have to figure out, in every new middle game, whether the 3-3 is currently the right move to play or defend against. |
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| Author: | jts [ Tue Sep 06, 2011 2:21 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
It's quite different from a monkey jump. If black makes a monkey-jump into white's territory, he has poked out about 5 of white's points and probably gained 2 1/2 points of his own. And he normally ends in sente, so we double the total. That's big, and fairly easy to calculate. If white makes a 3-3 invasion under black's 4-4 stone, he has taken about 14 points that black had some control over, and prevented them from becoming black's territory; he has gained maybe points of territory for white; and he has given black a thick wall facing the center. So in order to judge how much it's worth, you both need to judge how much black's thick wall is worth, and how likely black was to turn those 14 corner intersections into territory. At the beginning of the game, black might get half of those points by enclosing the territory, so we might say white has scraped off 7 black points; but on an empty board black's wall will be worth as much as three points per stone, or 18 points. So white has actually lost points with the early invasion. On the other hand, at the end of the game if black (or white) already has a large group near the corner, this wall will be nearly worthless, but perhaps all of the territory would have become black's after another move defending corner. That makes it worth 24 points or so to invade (and then double that, remember, because W keeps sente). So what are the two differences between invasions and reductions (for example, between the 3-3 invasion and monkey jumps)? First, in an invasion you make points inside your opponent's potential territory; the more likely this was to be his territory if he had added another move, the more valuable it is. Second, in an invasion your opponent can thickly seal in your stones, and you need to subtract the value of this thickness from the value of your invasion. On an empty board this is worth a lot (and worth even more if he has an extension a long way away), but on a crowded board it will be worthless. |
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| Author: | Redbeard [ Tue Sep 06, 2011 2:29 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
Look for The Big Move. It is time to defend against the 3-3 invasion when you have sente and it is the biggest move on the board. How do you know when the 3-3 is The Big Move? That's where reading and judgment come in. 
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| Author: | Ortho [ Tue Sep 06, 2011 2:53 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
Thanks for these replies! I knew I should defend it 1 move before white invades! From the point estimates there, I can see how this can be a somewhat delicate decision, but I can improve immediately by just defending it much sooner. I've had a couple of games recently where I've already built a big black wall that is now rather useless for whatever reason and lost 3 of the 4 corners in the endgame, because I've just never defended against it. Thanks! |
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| Author: | judicata [ Tue Sep 06, 2011 3:02 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
As others have said, there is no easy answer. If you find yourself making smallish moves and your 4-4 is lonely, consider it. If there is an urgent move (e.g. life & death) somewhere, then don't. Just food for thought, depending on what is happening on the rest of the board, this 3-3 can be quite nice: This is a label for the diagram. |
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| Author: | Bill Spight [ Tue Sep 06, 2011 6:53 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
The first pro game that I kibitzed was between two 9 dans, Takagawa and Yamabe. At one point Yamabe appeared to be in agony. He sighed, he moaned, he said, "I've lost." He grabbed his head, he swayed back and forth. Finally, after several minutes of this, he invaded on the 3-3.  It's not necessarily an easy choice for pros, either.
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| Author: | jts [ Tue Sep 06, 2011 7:05 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
Not to disagree with judicata - that's certainly a big move... but: This is a label for the diagram. ...it's not as though this is bad for black. In fact, this is great for black. This, on the other hand, is supposedly a little cramped: This is a label for the diagram. So "block the corner when you have a double wing formation" is good advice, but not quite so urgent as "block the corner when you have a low double wing formation". |
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| Author: | judicata [ Tue Sep 06, 2011 7:40 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
jts wrote: Not to disagree with judicata - that's certainly a big move... but: Yeah, but let's look at the alternative. What does black look like when white invades the formation AFTER black plays the 3-3. Of course, as I said, it depends on what is going on elsewhere on the board. Your second diagram is cramped because you shouldn't be making a low double-wing in the first place (insert normal caveats); you probably won't have time to play the 3-3, as a white stone will already be there .
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| Author: | Ortho [ Wed Sep 07, 2011 12:46 am ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
This is the kind of position I am talking about. I want this to be black territory. Black seems way ahead. White's area looks big but black has a lot more. The walls are already built. Obviously, the 3-3 invasions in the corners are only going to favour white. Is this a good spot to defend the 3-3 invasions or should it be even earlier? Position at move 83 |
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| Author: | Dusk Eagle [ Wed Sep 07, 2011 8:05 am ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
3 of the four 3-3 invasions shouldn't work at all: These sequences are only suggestions, black can kill in other ways as well. So I wouldn't defend these. However, for argument's sake, let's say they work, or let's say black wants to play it safe since he is far ahead of white by this point. Then, black should have defended a while ago. This is because if white invades and lives, black gets zero compensation for it. Whenever you're in a situation where you will get no compensation in influence on the outside if your opponent invades your 3-3, defending against the invasion becomes urgent. In this particular game, I'm worried most about the bottom-left corner, as it has the worst aji. Position at move 83 Therefore, I would defend this straight away: Position at move 83  is really passive, but it's probably worth it to ensure black holds on to his lead in this game.
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| Author: | snorri [ Wed Sep 07, 2011 9:11 am ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
Dusk Eagle wrote: These sequences are only suggestions, black can kill in other ways as well. Yes, but they are a bit above 16kyu I'd say.  This is one of those general things. The ability to use strong positions to kill invaders or really to do anything interesting at all is something that increases with playing strength and experience. The 4-2 point responses in a couple of your examples are severe, but require the external stones to support them. There is a kind of teaching game (see Biggest Corner in Senseis) where one side has a thick corner area other side tries to invade. For example: This is a good game to play with a stonger player. A kyu player can even play this with a pro because the difficulty can be adjusted. The weaker player can play either black or white. Play once with an 8x8 square. If white lives three times in a row, move the black stones in until black can kill. If white dies three times in a row, move the black stones out until white can live. (Like changing a handicap.) With this game, it is possible to develop a better eye for the kinds of sequences Dusk Eagle shows. I'm also concerned that in the game, it looks like black made the Butterfly shape: I'm not sure if this shape existed earlier in the game, but if it did, white can invade at  and live. If that is the case, then "defending earlier" for the OP might just mean making a better shape earlier...
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| Author: | Ortho [ Wed Sep 07, 2011 12:17 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
Thanks for these replies. I was really surprised that all those invasions should die! I sort of played out the 3-3 joseki by rote in each corner, figuring my extra move would help me kill the shape when it was finished off, but it didn't.  I don't really know the sequences to kill those, but I assume it's a matter of learning to read better than memorizing it, so I'll keep working on that Not playing the "butterfly shape" is something that I have learned as well. I'm going to ask a couple of the strong players at my club to play that invasion game with me for a while, as that looks exactly like what I want to learn. Thanks very much for the help! 
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| Author: | Dusk Eagle [ Wed Sep 07, 2011 12:57 pm ] |
| Post subject: | Re: When to defend against the 3-3 Invasion? |
P.S. Don't go getting the idea to play the shape below everywhere - it's normally very bad for black if white pushes through at 'a'. In my examples, it works because of the huge black walls directly behind it. Ortho wrote: I don't really know the sequences to kill those, but I assume it's a matter of learning to read better than memorizing it, You're right. I didn't have the sequences on the right memorized or anything, it was just reading and intuition. As you play more games your reading will become stronger.
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