Concept notes

Erasure 消し

An erasing move is a kind of large-scale forcing move with which you approach but do not enter the opponent's growing sphere of influence, forcing him to defend his potential territory. It is the opposite of invading. In general, weaker players tend to invade too much, and preen themselves if the invading group lives. They ignore the fact that the opponent may have allowed life in return for massive outside thickness enclosing the invader.

Stronger players, apart from avoiding this mistake, esteem erasing moves for two other reasons. One is that they are, in a sense, free moves. Like all forcing moves they can be discarded without qualms once they have done their business of making the opponent submit. The other is that the erasing moves can themselves turn into outside influence, though that is not usually the primary purpose, which is more to limit the opponent's expansion. Two of the proverbs listed below attest to the caution needed in developing from erasure stones.

The trick with an erasing move is to keep it shallow - not to venture too far. If you do encroach too much your opponent is liable to attack you from the outside, typically with a capping move, and turn you into an invader. Gauging the right spot is not easy - commentaries often refer to a "best guess". One heuristic is to play on or outside the "sector line" - the virtual line that joins the two extremities of the opposing sphere of influence, but even that can sometimes be too deep an intrusion. If you do get caught like this, your normal first priority is to escape to the centre rather than diving in deeper.

A further difficulty is that your opponent may even ignore your erasure and take the initiative elsewhere. You may later end up wiping out, say, a potential 30-point territory, but if you have taken three, or even just two, moves to do it, you have probably not gained anything. Indeed, the odds are that the opponent has strong positions on either side of the intruders, and later in the game he can use these to attack the intruders for a multitude of profitable endgame plays.

Ajikeshi, reducing potential trouble, uses the same verb but is otherwise not directly connected to keshi on its own. However, mention of it provides a useful reminder that erasing moves, like all forcing moves, can also blight future potential by strengthening the opponent, and so must be chosen with care.

Useful proverbs

• Asaku kesu ni wa katatsuki, boushi - To make a shallow erasure prefer shoulder hits and caps
• Boushi ni keima - Answer an (erasing) capping move with a knight's move
• Sayuu doukei chuuou ni te ari - In a symmetrical position there is a move in the centre
• Magusaba de rikimu na - Don't strut around in no man's land
• Nakachi wo kakou na - Don't surround the centre
• Kikashi to akushu wa kamihitoe - The difference between a forcing move and a bad move is paper thin

The most common word associated with keshi is probably asaku - shallowly. It is useful to keep in mind that all erasures should be shallow, that is modest.

© John Fairbairn & T Mark Hall (GoGoD), London 2008.