Probe
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A probe (Japanese: yosu-mi) is a play made in order to see how the opponent reacts. After a probe, the opponent must choose between one of two or three options. You should have planned your game so that none of these options are beneficial to your opponent. -- Morten Pahle
Also known as yosu-miru. See Yosumi vs Yosumiru. -- Eduardo Lopez H.
Mr. Yang Yilun, famous teaching pro, uses the term asking move. Probes usually ask the opponent to make a choice, say between inside territory or outside influence, which allows you to decide your strategy accordingly. --Bob McGuigan
Dieter Verhofstadt (1k) starts with a classic example of a probe given by Goran Siska and continues.
Possible local answers for Black range from a to d. I'm less sure about d, so I'll discuss the other three here in more detail.
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.
Charles here isn't usually correct by pro standards, even though it appears in a number of books: see probe popular misconceptions.
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.
Dave Sigaty: 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.
chooses to protect the corner. Either 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.
Dave Sigaty: 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).
Charles Matthews In fact the common answer from the pros to White now at a is Black at b.
Bob McGuigan: 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.
This is the commonly-used probe in the small high enclosure.
This allows White to get two useful moves and
and start to build on the outside; there is another common way to play with
at
.
Yosumiru Example From Pro Game 1
- Example moved to intermediate play - side example.
- The ultimate probe.
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