Cutting the Keima Keima
This is a keima. It can be cut at a or b.
Surrounding stones are critical
Cutting a keima
After the cut with and , White may capture the cutting stone in a ladder. So, cutting a keima is only practical when enemy stones (such as ladder breakers) are present.
Cutting Through a Keima
Cutting through the knight's move, with support
Cutting through the keima
Here White cuts through Black's keima, supported by an existing White stone. However, after , Black can capture in a ladder. The prerequisite for successfully cutting through the knight's move is that the ladder doesn't work.
Another Example
Another example
Here Black cuts through White’s keima. (The stones have been rotated 90 degrees so that position of the original keima remains the same, even though the location of the supporting stone of the attacker (White in the first case, and Black in this case) is different.
Pinwheel
If the ladder doesn't work, both sides can strengthen their weak stones to end up with this pinwheel formation.
Bad cut of the knight's move
Since the first cut depends on a ladder, White may be tempted to cut through the keima this way. After , there is no ladder. However, there is another drawback. In comparison with the "good" way of cutting, where White's stronger group forms a simple connection, here White forms a (weak) diagonal connection, encountering a (strong) simple Black connection. Hence, this way of cutting is not preferred. This is not to say that it will never be the solution.
Tsuke-koshi (Waist cut)
The waist of the keima
If there are enemy stones near the circled points, the spot farthest from the enemy stones is called the “waist of the keima.” (The Japanese term tsuke-koshi means “attach across.”)
Tsuke-koshi (Waist cut)
Black is the waist cut (tsuke-koshi ), striking across at the waist of the keima. The basic technique for White is to answer with hane at a, not push through at b. makes the initial cut
hanes on the outside
This ( and ) is not necessarily the continuation, but by playing the hane away from the position, White limits the loss to .
Pushing through the middle
To push through is usually bad. Black cuts easily with
Tsuke-koshi (Waist cut)
and now two white stones are cut off.
Not cutting at the waist
Not striking at the waist of the keima, but cutting at as in this diagram is zokusuji (vulgar play). White's natural moves are good moves: blocking at , and either sacrificing in order to make shape as in this diagram, or extending as in the next diagram.
is considered to be vulgar play, but striking at the waist of Comment: Not exactly sure why the keima does SEEM to produce a stronger, cleaner cut with better shape for Black.
Extending
If the surrounding position is strong enough, White can extend ( stretch). This is unlikely to happen, however, for if White’s surrounding position was strong, Black should not have attempted to cut through the keima in the first place.
Cutting Through an Oogeima
Large knight's move (oogeima)
Cutting the oogeima
Cut without any support
The basic technique of cutting a large knight's move in isolation is by attaching to one of the stones.
Bad cut of the large knight
Bad cut of the large knight
This is the bad way of cutting: Now either a or b can be captured with a ladder. (Functionally, this is the same as getting caught in a double-atari.)
On the side
On the side
On the side, the large knight's move very often goes from the third to the fourth line, keeping balance between development and stability.
Cutting on the side
Cutting on the side with the previously described is not possible. Black will be captured.
Taking away eye space
However, it is possible to take away the eyespace of the white group, by playing to . After , White can play a double hane at a or stretch at b. Depending on the surrounding stones, can become a successful invasion.
The oogeima in relation to one enemy stone
Taisha Joseki
This move is known to invite the taisha joseki. In general, there is one best way for Black to cut White’s large knight apart:
After Black will choose where to connect and White will likely cut the other side, but her marked stone can be caught in a ladder. (In the corner, the sides play an important tactical role, so there White may be able to get away with this move. In general, though, White’s move is aggressive and assumes a certain superiority in this area of the board (such as ladder breakers).
If White hanes on the outside instead
If White hanes at the outside instead of the inside, hazama tobi of and in a natural way.
is a very painful move, splitting White's
Cutting the Ogeima
Cutting an ogeima with no supporting stones
An ogeima can be cut apart without any supporting stones. Black through cut White, and although White threatens a ladder with , Black has sente and can avoid this.
Cutting an ogeima with a supporting stone
Here Black has one supporting stone to assist in the cutting of White’s Oogeima. The result is a pinwheel shape.
Tobi-tsuke (jump attachment)
Degiri (push and cut)
Keima tsuke
Don't Try to Cut the One-point Jump Cutting a one-point jump
The diagram shows what happens if White cuts the one-point jump in absence of supporting stones. (Black can of course play at ). threatens a ladder at a, but Black may well play differently depending on the board. In general, White will struggle to keep both , , and alive. This is why, in general, you shouldn't try to cut the one-point jump.
Comment: Even when is at the edge of the board, this approach doesn’t work. If White tries to trap at the edge of the board with a move directly below it, Black at a easily captures and .
Of course, if the cutting player has TONS of supporting stones around, cutting the one-point jump is possible. But in that case, the opponent would use a direct connection instead of a one point jump. So the point is moot. Don’t try to cut a one-point jump.
Another Example:
Typical one-point jump
An unreasonable cut
(If circumstances permit more aggressive fighting, could also be at a.) Black gets good shape. While White is busy defending and , Black's shape will get even better.
First diagram
Second diagram
White attempts a ladder
If White attempts to create a ladder with , Black captures (against the left edge of the board), and now Black has a secure base on the side of the board. Compare this result with the original situation. Not a viable move for White. Conclusion: Don’t attempt to cut a one-point jump.
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