Concept notes

Moyos  模様

Even though words exist in Korean and Chinese with the same characters as the word, moyo is really a special usage evolved by Japanese go players. The base meaning is pattern, design or framework. The go meaning is really an abbreviation of jimoyou, territory framework, or oomoyou, big framework. These terms are also used when a bit of extra precision is needed. One way or another, you can see that there is an element of structure surrounding a lot of empty space. Territory! No. Virtual territory, perhaps, to use a term coined by Matthew Macfadyen. But not plain vanilla territory (unless you get lucky).

The way to think about owning a moyo is to divide mentally into two areas (and if you can't do that it's not a proper moyo). You can assume that you will get one of these areas, but the opponent will destroy the other. The ideal trick is to get your opponent to invade one area and let him live small there. Harassing him as he lives will create a huge or strong wall that seals off the other area - which is your territory. You also end up with sente.

In pro games, such invasions are rare. The usual way to deal with a moyo is to reduce it, a specialist term meaning to play from the outside, pressing the moyo down towards the edge. This solidifies some of the moyo into territory, of course, but nothing like as much as the invasion option. Other benefits for the reducing side are that he keeps sente, he has a light group that can run away lightly and can be part of a sacrifice strategy, or that can be used for aji. In some case, the stones pressing down can do work of their own on the outside, forming a useful wall.

With such a nebulous concept it can be hard to evaluate a moyo. Counting half the whole area as likely territory is one crude way. Another, from Korean amateurs, is to count each key stone in a moyo as six points. Or you can do what Takemiya does in simul games: just poise your hand over the area and smile!

Prevention is better than cure. It's good advice to reduce a moyo one move before it is completed, or to send in a probe one move before. If you time it right, you can reduce on the outside and then invade - a common tactic in handicap games (the 3-3 points being the focus here).

Useful proverbs

• Asaku kesu ni wa katatsuki, boushi - To keep a moyo shallow, reduce with shoulder hits and caps
• Ippougo wa kiken nari - One-territory go is dangerous
• San-san ni uchikomi ari - Invasion at the 3-3 point is always possible
• Magusaba de rikimu na - Don't swagger about in no man's land

© John Fairbairn & T Mark Hall (GoGoD), London 2007.