Semedori
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Semedori is a situation to be avoided in which you are forced to play inside your own territory to capture and remove dead enemy stones, thereby reducing the value of killing the stones.
In this example, if Black plays first at a, he makes a point there and has eleven points. If instead White plays at a, she has placed Black into semedori, forcing him to eventually capture and remove the three circled white stones and reducing his territory to eight points. Thus this play at a is much bigger than it might look at first glance. In a real game, forcing a semedori could be worth even more, depending on the number of liberties the group that you force the other side to capture has.
Another example, albeit highly contrived. White is alive, of course, and the stones are dead, but if Black plays at a, since the upper group has only one eye, the result is a semedori situation requiring White eventually, once Black fills the surrounding liberties, to play three extra moves inside her own territory, at the marked points, to capture and remove the
stones.
Although semedori could be created by a crafty tesuji, more often it's a result of a complex middle-game battle. And because semedori often arises in the endgame, some assume it is an endgame-specific phenomenon, but actually it can occur at any point in the game (although normally the stones will not need to be removed until late in the game, as dame points are filled).
But here is an example that is an endgame semedori-based tesuji, from StrangeEndings. Black can reduce White's corner in sente using the semedori principle, by playing . White has to fill at the marked points and eventually capture and remove
and
, for 5 points of territory. If White plays the reverse sente at 1, she gets 6 points of territory.
The Japanese term, written 攻め取り, literally means "attack and capture". An alternative Japanese term is uchiage (打ち上げ), literally "play and take off". If a native English term is preferred "forced capture" is possible.
See /Discussion, much of which has now been reflected in this page.
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