2-4 Probe against a low corner enclosure
Table of contents | Table of diagrams The probe Block the probe from the outside Reinforcing the outside No escape to the center Shimamura's play Continuation Blocking the probe from the inside Pulling back |
White probes against the low corner enclosure. Local answers are hane at the outside (a) or inside (b), or stretch at the ouside (c) or inside (d).
[1] Blocking outside
White crosscuts with and plays kikashi with
and
. Then White jumps out lightly with a, if this was a reducing manoeuver. Alternatively White leaves the situation for the moment and plays tenuki. Later in the game, the stones at
,
and
will affect events at the top and in the center.
here isn't usually correct by pro standards, even though it appears in a number of books: see probe popular misconceptions.
[2] Reinforcing the outside
If Black thinks the outside is important, all outward aji will be removed by playing at . Naturally, this leaves the aji of White living in the corner with a. See the Tripod Group. With Black's territory reduced from the inside, White can now play a gentle reducing move, in case Black builds a moyo at the top.
Of course, B can respond to the hane later not by blocking it and forming a tripod, but by bending around the other stone with magari.
White may also push more aggressively at b. If Black answers at c, White plays a threatening to live with a better result than the tripod group. If Black answers instead at d, White plays c and escapes on the outside. This is discussed in The 1971 Honinbo Tournament, chapter 13.
Note that white should return to a, forcing black y before black gets one or more stones around x.
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.
This follow-up sequence is still being played in pro games.
From Black's point of view, White has played on the unintended top side. As ever with middlegame joseki, nearby stones have a vast effect on the judgement of the result.
[3] Blocking inside
chooses to protect the corner. White continues with a, probably reverting to answer 1, or plays tenuki. The aji of
enables White now to invade deeper than if Black had answered with
at a.
Another continuation for White is the clamp at b. In Strategic Concepts of Go Nagahara gives the continuation Black c, White d, Black a, and White e. By removing the stones at ,
, c, and b, Nagahara shows by tewari analysis that Black has played at a in answer to White's probe at d - an unfavorable exchange (in the position shown in the book).
In fact the common answer from the pros to White now at a is Black at b.
[4] Pulling back
Pulling back with is a common answer to
when Black wants to give White as little help settling her 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 a. Black will then usually pincer at b (if he doesn't already have a strong stone in that area) or play on top at c.