2-4 Probe against a low corner enclosure

The probe  

White probes against the low corner enclosure. His intention is usually to stop black from making territory in front of his shimari. Because the corner starts out as black territory, white has to play light and flexible. His stones will often end up being light or even downright sacrificed.

Local answers are hane at the outside (a) or inside (b), or stretch at the ouside (c) or inside (d). Finally the extension at e, though less common, is also played enough to be considered joseki.

Outside block  

If black blocks on the outside with , white will play the crosscut of . Although books tend to focus on another variation (see below), is by far the most common move for black. In this very standard sequence, black secures the corner territory, while white moves away to get some breathing space. The sequence from to is quite straightforward, though white might try a or b instead of .

book sequence, but rare  

The move most often shown in the books is . In professional play it is not non-existent, but it is rare, being too territory-oriented and foregoing a chance to put pressure on white.

After , it would be a mistake for white to play at a though. As they stand, white's stones are light and easily discarded, but playing at a makes them heavy. Instead, white should jump out lightly, for example at (the exact location depends on the position) or even play tenuki. White should treat his stones at , and very lightly. Black has answered them on the inside, so they are easily sacrificed.

See also probe popular misconceptions.

change of pace  

There are two more possible continuations for black. leads to an exchange, where black takes the position at the top that white was trying to avoid, but at the cost of not only giving white the left side, but also losing some of the corner territory.

change of pace  

followed by is usual when the white stone at is present. After the usual move at or an immediate atari at , ends up in a useful position. The exchange of for makes white heavy. If black plays immediately, then plays atari at after ----tenuki, white will probably play at a, not at .

Reinforcing the outside  

After , white has two answers, and a. In both cases black still can choose between the corner and the outside. With , black takes the corner. The sequence continues to , followed with at or b. The continuation after that depends on the surrounding situation.

Taking the outside ( to at a-b-c)  

The combination of and may be due to Shimamura Toshihiro in a 1950 Oteai game against Takagawa. This sequence occurs in the 1971 Honinbo Tournament book, with the attribution to him (but no game reference).

The idea is that White cannot now live in the corner. The stone is not for taking.

No life in the corner ( at , captures, at a, at b)  

This diagram shows that white cannot take the black stones by playing in the previous diagram at here. After , the white corner group is dead.

A modern variation, but why?  

A more modern variation (I see no occurences before 2010, but it has become the more usual move since then) is for black to play immediately. White answer with at , or . There must be a reason for this move, but I don't see it. If white plays here, the variation converts to the previous one, so my feeling is that black is only giving white extra options.

Preparing to attack  

Playing instead of a looks like a quiet, submissive move. But in this case, at least if there is a stone at or around that spot, looks are deceptive. Black is just avoiding any weaknesses in his position, so that he can all the more forcefully attack white with and the following moves.

White gets the corner  

If white plays , followed by , white will get the corner (see for an exception further down, however). White lives comfortably in the corner, but black gets outside strength in all directions.

A small life  

If white does not want to provoke and in the previous diagram, he can also live with here. Note that after , a is black's sente.

Black plays hane  

If black blocks with , white usually reverts to . After , the aji of the white stones in the corner give his an advantage in the fight at the top by making any of the points marked x his sente.

Tripod group  

White could also play here, after which he lives by creating a tripod group. This is however more a joseki for books and amateurs. Professionals tend to play this way only when there is not enough room to live on the upper side.

Under attack  

is another book move that is more usual among amateurs than among professionals. The idea behind this move is that the white group is left out into the center, but there will be heavily attacked or even killed.

Another attack  

In professional play, the more usual way to get a similar result would be and here. Again white cannot live in the corner, and is facing a tough fight in the center.

Blocking from the inside  

chooses to protect the corner. White forces once more with , then lightly jumps out with or some such point. White could also play around or even play tenuki immediately, satisfied with having around for future use.

Clamp  

Another continuation for White is the clamp at . In Strategic Concepts of Go Nagahara analyzes the result of the joseki in this diagram. By removing the stones at , , , and , Nagahara shows by tewari analysis that Black has played at in answer to White's probe at - an unfavorable exchange (in the position shown in the book).

Pulling back  

Pulling back with is a common answer to when Black wants to give White as little help settling his stone as possible. This leaves White with few forcing moves. If Black has a strong position in the middle of the upper side this can lead to a strong attack on . A standard response by White is a hane at . Black will then usually pincer at (if he doesn't already have a strong stone in that area) or play on top at a. If the attack in this diagram is too powerful, white should play more lightly with a move around b instead of , keeping for later use.

Pulling back  

has the same intention as a, giving white as little help as possible in settling his stone. White will usually jump out with a move like (although sometimes is played at immediately), black's answer depends on the position on the top and exactly which move white has chosen. is an important point for both. If white plays it, black has to answer at a, because giving white living stones at both the top and the corner is a clear loss for black. Still white is often not in a hurry to play it, hoping to get a chance to play immediately in the corner at a or b, so black might be able to play even though for him it is gote.