4-4 point 3-3 invasion, extension
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The 4-4 point 3-3 invasion simple extension is a common and popular modern joseki ever since the AI revolution. It is a basic move that is played at all skill levels, is well-regarded by strong AI programs, and emphasizes taking sente. While it may not be the strongest local response, forming a three-stone wall is good shape and resilient, so it can be a good choice if Black intends to tenuki.
White's main options are to (A) jump ahead or (B) push. Tenuki is not advised.
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Moves are listed by frequency in professional games, which is sensitive to whole-board position. Bolded moves are commonly considered joseki.
- a, 4-4 Point 3-3 Invasion, Extend, Small Knight - (joseki) (common) (beginner) (AI favorite)
- b, 4-4 Point 3-3 Invasion, Extend, Push - (joseki) (common) (beginner) (AI favorite)
- c, 4-4 Point 3-3 Invasion, Extend, One-Space Jump - (joseki) (common) (AI favorite)
Overview of Joseki
Jump, Push and Cut
- White jumps ahead with the goal to quickly settle the position in a stable shape. The follow-ups are not particularly urgent for either player. Black will end the joseki in sente, so playing this way discourages Black from continuing first in the corner.
- The small knight is typically considered the default move. It has few weaknesses and white's group is comfortable.
- If white possess the ladder, they can play the one-space jump. Please note that the one-space jump can always transpose into the 3-3 Invasion, Double Hane Joseki regardless of the presence of a ladder.
Push, Small Knight
- White can opt to push, which typically reverts the three-stone hane shape. The three-stone hane shape is a slightly more unstable position, and both players would prefer to get the first follow-up in the corner. Normally, Black ends the joseki in sente, so typically the three-stone hane shape is slightly more desirable for Black. White may play this way if they believe they will get the first follow-up (i.e. Black has an urgent move elsewhere on the board).
- In response to , Black hane with is the standard move. However, Black may opt for a non-standard move like extend when it seems like White will return to the position first and the surrounding environment seems unfavorable for Black. In particular, Black should pay attention to the potential cut and fight at a, which White may take if they are strong in the area.
Pay attention to the ladder for the one-space jump
If the ladder favors Black, Black can ladder the stone as depicted above.
Black's group becomes very strong and White has been sealed in on both sides.
If White attempts to play a ladder breaker, Black will often play somewhere around a or simply capture at b.
Jumping ahead vs. Push?
To illustrate the considerations when deciding between jumping ahead or to push, Oh Yujin (6p) vs. Wang Chenxing (5p) (2019) teaches us some useful principles. In the depicted game, white approached the top right corner with , but black chose to tenuki and instead invaded the top left corner with .
We can clearly see that black owes a move at d, so sente is especially valuable in this board position. White played a sente corner variation with , and now it is black's turn to move.
Should black play at a, b, c, or d?
at d is not possible. Black should not tenuki from the top left corner.
at c is a valid option because black possesses the ladder. However, is it a good idea?
If black jumps ahead with a or c, it is obvious that white will play at d to double approach the top right corner, which is an unpleasant outcome. White has already profited, but black has very little to gain. The jump ahead shape is very stable for both players, and there are no other big moves left on the board.
Instead, Oh Yujin (Black) opts to push at b. This move fights for sente in the sense that it dares white to create the unstable three-stone hane shape. White cannot play in both the top left and top right corners at the same time, so they must choose between the valuable local continuation on the top left or tenuki to double approach the top right.
Whichever one that white chooses, black can take the other.
Tenuki is not advised
White tenuki is almost always a mistake. The corner becomes a ko for life.
Black can atari at a to initiate a ko. However, black will lose sente by offering the ko. It is white's privilege to start the ko whenever they like, so sometimes skilled players may choose to defer the atari when there are more valuable moves on the board.
Alternatively, at b permits white to live, but white will live in gote.
-  Frequency statistics were obtained from Waltheri's Go Pattern Search using the full database restrained to a local search (accessed September 2021).