Preventing escape on the first line

  Difficulty: Beginner   Keywords: Life & Death, Tactics

In the early stages of learning Go, beginners will start to appreciate that preventing a surrounded opponent's group from escaping is usually not an easy matter. For example, how to prevent the opponent from escaping from the first line? Figuring this out may not be so easy, but fortunately, this is a situation that is easy to explain and understand. This article specifically explains how to prevent escape on the first line.

Table of contents


Warming up

Let's warm up with a really easy case. If this is superfluous to you, just skip to the next section.

[Diagram]
Black cannot escape  

At the corner, Black has only one eye - that of a straight three. We show that Black cannot escape to the outside and hence cannot avoid capture. In other words, Black is dead.

[Diagram]
Black cannot escape  

If B1 tries to escape towards the right side, then W2 easily blocks and Black has no way out. Similarly, if B3 tries to escape, then W4 blocks with a tiger's mouth, so Black has no way out.


Hane

One way the opponent can try to escape is via a hane on the first line.

[Diagram]
White to prevent Black's escape  

Black just played the hane at black+circle. How to stop Black from escaping?

[Diagram]

Easiest to understand

Perhaps the first way that comes to mind is to continually pull back with W1, W3 and so on.

[Diagram]

Easiest to understand

This no-brainer approach continues.

[Diagram]

Easiest to understand

At the end of the day, Black will run into the opposite corner of the board, and the opposite edge naturally stops the escape.

[Diagram]
Not so nice  

However, in real games, things are rarely so nice. Chances are, at a certain distance away, there are some Black stones, such as the black+square stone in this diagram.

[Diagram]
Not so nice  

In this case, merely pulling back every time is not going to work. After B8, the corner Black group gets connected with the black+square stone, so the corner Black group is suddenly alive again. Therefore White needs a better way of stopping Black from going out.

[Diagram]
Atari  

In this case, White can directly block at W7, which happens to be an atari on the line of Black stones. If B8 connects, then W9 defends against the cutting point. Now Black is totally surrounded. (And has lost some extra stones, as well.)

[Diagram]
Capture  

If B8 tries to cut, then W9 simply captures the Black stones, and it is game over for Black. (At least in the top left corner.)


Hane, again

Having understood the previous case, we now explore another case of the hane.

[Diagram]
White to prevent Black's escape  

This case is very similar to the previous case, but there is a very important difference.

[Diagram]
Ko  

If W1 makes the same atari as before, then Black can make a ko.

[Diagram]
Ko  

There is no way to avoid the ko, because B2 and B4 is the elementary first line capture technique. Further, B6 may elect to use a net instead.

[Diagram]
No escape  

But if White pulls back once and then ataris, White captures two stones, and there is no ko.


Pushing out from a descent

The hane was easy because it is possible to atari. Now we explore a harder case.

[Diagram]
White to prevent Black's escape  

When Black pushes out from a descent, White can no longer atari, so it is more difficult to prevent the escape.

[Diagram]
Pulling back  

If Black has no second line stones to help, White can just pull back as before.

[Diagram]
A black stone on the side  

If Black has a stone on the side, White can prevent escape by jumping out.

[Diagram]
Push  

Timm: Black B2 in the previous diagram (one point jump on the first line) is the “submissive” answer. This one is slightly more tricky.

[Diagram]
Push, extend  

However, White can revert to the previous situation with this W3.

[Diagram]
Push, block  

White can also be more severe but the cut may be problematic, depending on the situation.


Exercises

Here are two exercises on the methods for preventing escape on the first line.

[Diagram]
Exercise 1: White to kill  

White to kill. That is, White to prevent Black from escaping as well as living.

[Diagram]
Exercise 2: White to kill  

White to kill. That is, White to prevent Black from escaping as well as living.


Solutions to exercises

[Diagram]
Exercise 1: Analysis  

Note that a Black move at a is sente, in the sense that the next move at b makes two eyes. Therefore, this position should be treated like that with a descent at a.

[Diagram]
Exercise 1: Solution  

A solution to Exercise 1 is to jump at W1. If B2 attaches underneath, then W3 and W5 finishes the job. We leave it to the reader to figure out why W3 at a is a mistake.

[Diagram]
Exercise 1: A questionable play  

[Public Neophyte:] What's wrong with playing at a here?

Anon: Black gets to escape at b.

Joe?: But white can then capture the black stones by playing next to a, preventing two eyes. (Next, the two stones are captured by black, and a is played again.)

TheBigH: Then black can capture the new 'a' stone, and this connects the 2nd line stones to the ones crawling out on the first line. The problem is still how to prevent escape; assuming I've understood your question right.

Joe?: See here: [ext] http://eidogo.com/#1J3E67szL The false-eye shape can then be captured.

TheBigH: You said white plays next to 'a'. Your linked sgf does not have that variation. Like Slarty said, doing that would be an error. [ext] http://eidogo.com/#21jX7sgsW

[Diagram]
Exercise 1: Alternate Solution  

Slarty: It's ok to play there first, because after B2, W3 still works to prevent escape. It's nearly the same. The corner is dead as is. W3 at b is a big mistake; black would ignore to play 3.

[Diagram]
Exercise 2: Analysis  

Observe that a Black move at a is an atari on three White stones, threatening to capture at b. Hence this position should be treated like the second kind of the first line hane.

[Diagram]
Exercise 2: Solution  

A solution to Exercise 2 is to pull back at W1. This avoids the possibility of having to fight a ko.


See also


Preventing escape on the first line last edited by Timm on June 18, 2014 - 12:45
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