Concept of a territory is one of the central in Go — after all the entire game is a struggle for it. Definition of a territory is deceptively simple — it is an empty space surrounded by an uninterrupted line of stones of the same color (only horizontal and vertical holes are considered to be interruptions). It is important, however, that stones surrounding the territory are "alive" — empty space surrounded by the "dead" stones is not a territory — such stones are removed from the board upon the game completion and are added to the "prisoner" stones (Basic rule 10).
In the process of struggle for the territory stones of both players intertwine on the board in complex combinations, and it is extremely important to be able to tell the "live" stones from the "dead". The decision might be complicated by the presence of the opponent's stones within a potential territory.
To formulate the generalized concepts of "live" and "dead" stones it is helpful to review a series of characteristic positions. Reviewing of each position amounts to analysis of all possible moves for each player in a given position.
Position 1 | ||
Position 2 | ||
Position 3 | ||
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Position 4 | ||
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Position 5 | ||
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It is possible to make the following conclusions basing on the above analysis of characteristic positions:
Note: |
Groups of types 3, 4 and
5 are "alive"
(conditionally or unconditionally) only with the provisions of the right
moves of the player in reply to the opponent's attack. These groups
might also "die" as a result of a Ko-fight,
which is discussed separately. If a possibility
of a Ko-fight is to be taken
in consideration (and in the real game it should always be), then the
only absolutely "alive" groups are those having at least two
"eyes" — anything less formidable than
that can be captured. It's not practical, however, to waste moves
on making the actual "eyes" in the positions
with more than one "critical"
points, since each move is valuable, and presents an opportunity to the
player. The proper balance of the opportunities might be a
protection almost as strong as two "eyes".
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