When and wherever explaining kikashi, the following joseki always seems to be given as a prime example:
The sequence from 1 to 17 in Dia 1 is a fairly often seen 5-4 point joseki. White takes corner territory in sente, black in exchange building outside influence with his stones. The exchange of white 1 to black 2 in Dia 2 is assumed to be part of the joseki, and after black 2, play usually moves on to another part of the board. Most readers can probably classify white 1 as a kikashi, or as a forcing move, but what exactly happened here?
When asked for justification for white 1 in Dia 2, an oft-heard reply is that "white 1 is sente, because black has to respond with 2, and then ▲ is forming a bad empty triangle". This is correct, although not the whole truth. White 1 can also be said to be a "peep", or nozoki in Japanese.
What if black resisted, like with black 1 in Dia 3? In that case, white could cut with 2, and if black played a counter atari with 3, white is able to make the larger cut of 4. After 6, the result would be a disaster for black in most games.
Instead of black 3, black could play at 6. Then white would have gotten some extra territorial profit in sente, also being able to continue at 3 later.
What if black played the solid connection of black 1 in Dia 4, preventing the white peep? Later in the game, white would be able to capture a black stone with white and 4, leaving a cut in black's shape at A. If black used his turn to prevent the cut with black B, white would again have profited in sente. Looking back at Dia 1, the black hanging connection of 17 completely prevents the cut of A in Dia 4. For this reason, black 17 in Dia 1 is the joseki move.
Looking back at Dia 2, white 1 is indeed sente, and a peep, but what makes it a kikashi?
If "kikashi" meant the exact same as "forcing move", the term kikashi wouldn't have to exist at all in western go culture. The terms aren't exactly synonymous, however. The Japanese word kikashi, 利かし, uses the character of 利, which stands for "benefit" or "profit". In general Japanese language, kikashi more often means "to season" or "to enliven", but it also has the meaning "to bring out a thing's effect", which hits the jackpot for us. The verbs 利く ("kiku") and 利かない ("kikanai") also come up in Japanese go language, apparently meaning "forcing" and "not forcing". They share a connection, but do not hold all of "kikashi"'s meaning.
I will have to attack the current Sensei's library definition of kikashi a little bit:
Kikashi, a Japanese go term adopted into English, is a sente move or sequence that produces a certain additional effect. Because it has done its work, it can normally be freely abandoned unless it is part of a much larger chain or group. It is usually translated as forcing move or sequence.
While not being wrong, I would imagine I am not the only one who finds this definition too ambiguous; what is exactly the "certain additional effect"? What about the second sentence in this definition — it can be abandoned, unless it can not?
Looking back at Dia 2, can the reader figure this out somewhat? White 1 is sente, and a peep, forcing black 2. While black got a bad empty triangle, it is not simply for the empty triangle that white 1 is kikashi. White 1 is kikashi because it can be used, more so than black 2: white 1 can be an effective ladder-breaker. This would be the so-called "certain additional effect" of our sample kikashi, here.
Let us have a look at another example. The sequence from black 1 to white 12 in Dia 5 is a well-known star point joseki. I'm sure many readers have seen black immediately push with black 1 in Dia 6, forcing white 2. I saw this kikashi example in the Japanese go theory book 依田ノート ("Yoda nooto", Yoda notebook), where Yoda Norimoto 9 dan discusses the subject. He quotes an amateur player who justified Dia 6 like this: "It feels good to get a one-point profit in sente, forcing the opponent to respond".
If black didn't play black 1 of Dia 6, black would have more options for the future. For instance, if black later on got a stone at 1 in Dia 7, and white didn't respond, black would have the tesuji of 3, which would reduce white's corner territory in sente — white would need to create two eyes with white 8, unless he were able to escape to the centre and live there.
Even if black wasn't able to get black 1 and 3 of Dia 7 in, he would still be better off to leave the kikashi of Dia 6 for a ko threat.
Still, black 1 in Dia 6 is a sente move that reaps a "benefit", reducing white's territory by one point. You could argue it to be a kikashi, albeit a bad one.
To further explain kikashi in words of one syllable, here's a third joseki example. The moves from 1 to 25 in Dia 8 are an old 3-4 point joseki. After black 25, white most often plays elsewhere.
Later in the game, black has the options of A and B as in Dia 9. Both of them are kikashi. Black A prevents white's advance to the centre in sente, forcing white to remove the three dead black stones off the board. Black B prevents white's advance to the upper side in sente, forcing white to remove the three dead black stones off the board. Black cannot get both A and B in sente: it's either-or.
It would be an amateurish mistake for black to simply play either A or B at the first opportunity. The correct way of play would be to first figure out whether the upper side or the centre is more important for black, and then pick the better kikashi. If neither kikashi was good for the time being, black should leave both of them unplayed until one became clearly superior to the other.
Indeed, kikashi are not simple forcing moves that are played because they can be played in sente, but we have to be mindful about what the kikashi's actual benefit is. For argument's sake, I wouldn't classify black 1 of Dia 6 as a kikashi: it, in fact, loses black much more than it gains, and to me, a "bad benefit" is an oxymoron.
A kikashi is a sente move that benefits the one who played it.
The sequence from white 1 to black 16, here, is another joseki. After black 16, white usually plays a move like B to counterattack black; even when white doesn't defend his corner group, black cannot kill him without a ko fight. Black 16 is increasing the black chain's liberties while threatening the ko (which starts with black 2-2 in the corner). If white answers with A, he will have responded to the threat black 16 made, and black 16 becomes a kikashi; black got a benefit, namely additional liberties for his group, in sente. On the other hand, if white answers with B or the like, he will not have responded to the threat black 16 made, and black 16 would not have been a kikashi.
A move is not kikashi unless the opponent responds to it in the predicted way.
Earlier I argued that if an attempt at a kikashi is not beneficial, it's not a kikashi. This diagram here features white 6, which at the time could be called kikashi, being sente, forcing black to respond in a predicted way, and reaping a benefit (strengthening the white 2 stone). However, after the sequence has been played up to black 11, the kikashi of white 6 turns bad: the exchange of white 6 to black 7 is beneficial for black. Black's way of play here is effective, having made white waste his kikashi. Similar techniques can be found in many a professional game.
There is a pseudo-proverb of "play kikashi before living". What is exactly meant with it? By now, the reader will already know that a kikashi is not a kikashi unless it reaps a benefit.
Let us look at the sequence from white 1 to white 17 in the diagram above. White 1 goes to live in what was originally sort-of black's corner, and black cuts white's stones starting with black 2. White's solid connection of 5 is a possible way of living in the corner: this way, white gets the kikashi of white 7. This is an example of "play kikashi before living". Black went out to cut white's stones, and white makes use of understanding black's intentions by playing 7, which simultaneously strengthens the white stone to the left and creates the possible white connection at 8. When black cuts at 8, white then moves on to live with 9 etc. White 15 is yet another kikashi, and when black has completed his dumpling shape, white finally lives in the corner with white 17. The white stones towards the left will not get in any trouble even though black was able to cut white.
Instead of the black cut of 8 in the earlier diagram, black should in this case play as shown here. Now, it is actually the ▲ stones that became kikashi, reducing white's territory!
Here's an artificial position where black has an opportunity to effectively play kikashi before living. Can you find it?
Before creating two eyes, black should first peep with 1 as shown here. If white responds with 2, black then creates two eyes, and he may get use of the cut of A later on, if the white right-side stones become attackable. If white responds with A to black 1, black would already be alive and he could play elsewhere.
A kikashi forces the opponent to commit more to his game plan, and so benefits at the opponent's expense.
This here is the game against the Japanese 8 dan which I already showed some weeks ago.
As the reader may guess, white 50 is meant as a kikashi. Black stated with 49 that he won't let white live easily, while also surrounding territorial profit in the upper right corner: white 50, then, is asking black to commit some more in his corner territory. Black has to be careful about his response.
If black simply defended with 1 as here, white 2 becomes a difficult move to handle. If black uses the common technique of the hane of black 3, up to black 7, white's result becomes excellent. White has A in reserve so that he can make two eyes for his group anytime he wants, but since the group already appears to be safe, he might as well play the sequence of white B, black C and white D next, going on to live on the right side. This way, white 50 will have become an excellent kikashi.
If black doesn't play the common technique shown before but something else, white will play as shown here. After black 11, white will have made his upper-side group strong, and while white 50 now isn't really a kikashi, it doesn't lose white anything either, as black also has the weird-looking stone of 1. Most important of all, this way the white upper-side group got strong in sente: this result is still a major white success.
For these reasons, in the real game I didn't simply defend against the white kikashi, but fought back with black 51 and so on. White would have been able to live in the corner, but in that case the upper-side white group would have gotten in serious trouble.
To start reaching a conclusion for this essay, I would like to wrap up the definition of kikashi as "A sente move or sequence which reaps a benefit while forcing the opponent to commit more to his plans." I may come back to this text to make minor structural changes to this definition, but anyone who has read this far should be able to see my intention behind these words.
More skilled readers may be interested in knowing that professional go is all about kikashi, and if a professional game's result isn't caused by a simpler mistake, the reason behind the result will more often lie in one or more successful kikashi.
Not too seldom, somebody finding a fine kikashi will transform entire joseki. Remember Dia 8 in the beginning of this essay?
In a fateful game between Go Seigen and Takagawa Kaku in 1957, Go Seigen diverged from the then usual large avalanche joseki (Dia 8) by playing black 13 in the diagram on the right of Dia 8. If white simply responded with 14 and proceeded to play the classic large avalanche joseki as normal, up to black 27, the exchange of ▲▵ nets black an extra two points. A two-point hard gain is huge in terms of professional go, and for this reason, the whole large avalanche joseki got transformed, more or less due to one simple kikashi.