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Cutting right through a knight's move is very big
Path: GoProverbs   · Prev: StrikeAtTheWaistOfTheKeima   · Next: DoNotPeepAtCuttingPoints
  Difficulty: Beginner   Keywords: Proverb

Karl Knechtel:

The keima (knight's move) usually provides a reasonably fast way of extending and in general won't be cut. After a strike at the waist of the keima, cutting on the other side isn't possible immediately because the opponent can be caught in a ladder:

[Diagram]
Trying to cut a keima

(Note that the actual "strike at the waist of the keima" proverb refers to the situation where there's a supporting black stone - see the page for details. It came to mind, though.)

Of course, with two moves in a row locally, Black can plough straight through. The idea behind my proverb is that doing so is usually a very big play in actual game situations, and thus B1 is sente and a big ko threat in many cases.

Why?


[Diagram]
Black is permitted to cut

When Black is permitted to cut, the damage is evident, though contrived.

  • White is denied a connection between groups above and below (in the given diagram - the 'knight' is 'standing up'), which White previously was entitled to.
  • Black is granted a connection between groups to the left and right which Black previously was not entitled to.
  • White's stones are placed badly; they're touching a stronger black group, and trying to support one white group lets Black target the other.

See also BQM23.



[Diagram]
Add one stone and ...

While locally the keima is quite strong, it takes only the marked black stone to ensure the cut - Yomiuri Shimbun's English language The Magic of Go column #179 is [ext] an article on this. -- lavalyn 17k



BobMcGuigan: The split knight's move, as in the following diagram:

[Diagram]
Split knight's move

is usually a very bad shape, but it often happens as a result of a ko threat that was ignored (see e.g. There are No Ko Threats in the Opening).

Black might have the knight's move shape already in place, and a ko starts somewhere else on the board. Then White might play W1 as a ko threat, Black might end the ko, and White could then play the stone marked with a square..

[Diagram]
corner





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