A history of joseki habits · 17
Why the Shusaku diagonal held an entire order together before komi
The Shusaku diagonal was never an answer outside history. Restore no-komi play, Black's incentives, house research, and later komi, and the same coordinate moves from steady to slow—then returns under AI for a different reason.
The diagonal drew value from its era before its name
After a low approach to the lower-right komoku, P5 does not chase White. It leaves Black a corner frame that is hard to break. Without komi, Black did not need to recover a compensation payment through immediate activity, so long-run stability converted directly into winning chances. The pincer in the comparison also uses only three moves, but buys a target instead: faster, sharper, and more dependent on direction.
Step through P5 and M3: the move count is identical, but one buys stability and the other an attackable stone. Efficiency asks how many jobs a move performs
A classical order may invest once more so the corner is difficult to exploit. A speed-oriented order spends that turn on an empty corner. The former reduces later reading cost; the latter increases present board coverage. Calling reinforcement slow does not mean it has no value. Komi and a more urgent opening simply raise its opportunity cost: while another corner is empty, the local move must prove that it cannot wait.
Move five reinforces the lower right or claims the lower left, exposing the exchange between certainty and coverage. House joseki was living research, not a public answer sheet
The National Diet Library's Go collection places joseki and difficult variations inside a culture of schools and transmission. The 1846 ear-reddening game adds a concrete warning: even Shusaku met a prepared taisha variation over the board rather than as timeless common knowledge. Books later stabilized combat into transmissible lines. This board is explicitly a reconstruction comparing continuous local investment with a whole-board pause, not the historical record.
The same six moves either enter contact fighting locally or spend only three nearby and preserve board-wide speed. AI choosing the diagonal again does not vindicate it forever
After komi, an immediate pincer often better matched Black's need for activity. Strong AI later returned to the diagonal in selected whole-board positions. The coordinate came back; the proof changed. It is now a low-risk option bidding against pincers, ladders, nearby strength, and sente—not a move made correct by Shusaku's authority. The useful lesson in an old joseki is the problem it solved under its own conditions.
Both boards contain the same stones. Different era and efficiency labels show why a coordinate is not an argument.
Historical and terminology sources
Before reading an old joseki
- Was there komi, and who held Black?
- Did the move buy stability or attack?
- Do outside stones and ladders support it?
- Is the board a record or a reconstruction?