The KIA is quite passive and black could create an attack quite fast however it is very hard to break the KIA structure
King's Indian Attack ok or not?

It is obvious to me that there must be some merits associated with the KIA. Otherwise, the strong players refered to above wouldn't have played it as frequently as they did. Dvoretsky even recommends it in Opening Preparation. Is it really passive? Sure, there is a slow build up. Agree.
Another thing I wonder about is the extreme similarlity with Closed Sicilian. Only c3 inserted instead of Nc3. To me, it is not obvious that memorizing 20 moves in the Najdorf will increase my winning chances. That's another side of all this, of course, the practical aspect. I am also interested in discussing the theoretical aspects.

KIA is typical of many system openings which are basically black openings reversed. The common trends would be unambitious pawn moves and doesn't fight for the center. I think the reason for this is that while these moves are often 'best' as the second player when white is making strong, sometimes forcing moves, they are really quite silly when taken out of context, for example as the first player. Playing a black opening reversed isn't really the proper way to make use of your first turn advantage, you're just giving black an equal game with no fuss, and making sure you have an uphill battle towards advantage. In short, it's like you're playing black yourself! - my 2 cents

Fischer was not the only strong player who played the KIA - it was played, with some frequency, by Petrosian, Spassky, Benko, Larsen, and others. Objectively the KIA may not give an opening advantage but it tends to result in complex middlegames that provide plenty of scope for the stronger player who has a better understanding of the positions to play for a win. I wouldn't recommend making it your only opening though.
I often use KIA in bullet (playing unrated, want to check mate, not to won on time)
It's not give white any advantage but prevent black from exchange material for a while, Which could lead to fun and complex middle games

Its not called the 'I cant play chess' attack for nothing...
I agree, the people that say it probably don't say it for nothing.
If your goal is to play only the best possible chess moves, taking the long view of how likely a structure is to favor your side with perfect play by both sides for the duration of the game, then you should probably avoid the KIA. The continuing history of chess theory and high-level computer analysis show that it's a tiny fraction less likely to give you a lasting edge against super GM level competition than the Queen's Gambit, Catalan, or Ruy Lopez.
If your goal is to win and enjoy chess games, the KIA is a brilliant choice. As are the Colle, the Barry, the Stonewall Attack, the BDG, and any other number of frequently pooh-poohed openings.
The fact that these openings tend to lead to arising structures where the correct plan for white is both consistent and clear means that most players' chances of playing "perfect" or even "good" chess moves as the game progresses are actually infinitely higher with these openings than with, say, a Catalan.
The failing of these openings is that they will never, ever hold up against super GM level competition. And if, for whatever reason, you feel that this is your destiny, you would be a fool to play like this.
Thus, the KIA is a poor choice and even a malicious recommendation for an under 10 player who is rated, say 1600-1800 or better.
No one rated lower than that at a very young age is ever going to reach a point where choice of opening matters beyond what you enjoy (and suceed with) playing. No one rated higher than that, at any age, is ever going to feel the need to ask such a question.

This is a newbie question, but in the example above, I don't understand black's decision on move 28. Why would you leave your queen completely open to attack there? I'm sure there's a reason, but I can't see it yet.

This is a newbie question, but in the example above, I don't understand black's decision on move 28. Why would you leave your queen completely open to attack there? I'm sure there's a reason, but I can't see it yet.
The Queen has no good square to move to while protecting h7.

And if you thought that the KIA was never played in a WCH match, or that a super GM could never lose to it...

I love how you take IM watsons word higher than WC bobby
Hi, I am not. I simply gave an example of an author (famous such) claiming that KIA is a toothless opening.
I don't know what I think, that's why I started this topic today. For one thing, I have tried to learn some open sicilian as white (e.g., studying Experts vs Sicilian) but it simply is overwhelming. I have too a little tima avaiable, and got into bad trouble several times, mixing up move-orders. So I switched to the Closed Sicilian, and got Emms book. And I tried KIA versus French.

The KIA is indeed toothless.
Dvoretsky showed how even a toothless openings such as the KIA can be interpreted actively. But he was only able to demonstrate that White has equal chances with best play by white.
I am not sure this is true. I had his book, then lost it; can't check it myself, but it seems highly doubtful that Dvoretsky would go "Look, you can play a bad opening as white and get equality with best play".
It doesn't seem plausible to me. Anyone?

Jesper Hall writes about KIA, and seems pretty serious about whites possibilities to create winning chances. (Versus the French, that is).
I am not saying KIA is good, only "Is it really so bad, when several well-known players claim otherwise?"
It's an easy opening to learn and fairly safe into the middlegame. A good opening for someone just taking up the game who doesn't want to study deeply yet.

And if you thought that the KIA was never played in a WCH match, or that a super GM could never lose to it...
It's used for surprise value only and to play to the opponent's weaknesses. No GM would use it as a serious opening, that was practically the only time Karpov ever played it. It's fine to use as a back-up plan or as a surprise opening, just as long as it's not your main opening.
But by all means, use it as your main opening if you want. Me and people like me will be only too happy to equalize as white and take advantage of your complete lack of true opening knowledge.
I don't actually use it as my main opening, and I am pretty sure that my general openings knowledge is better than yours.
Are you sitting inside GMs heads to know that, even when they are playing an opening in an important match against a top opponent, they are not playing it as a "serious" opening ?

Atos' post #12 is precisely the sort of argument that fails miserably. Fischer did indeed play, and win with the KIA. He even played it relatively late in his career.
But against the Sicilian, his favorite variation was the Open Sicilian. You don't see these KIA afficionados recommending the Open Sicilian main lines "because Fischer played them".
When Fischer played the very best in the world as White in the Sicilian (Taimanov, Petrosian, Spassky), he chose the Open Sicilian.
You are construing an argument where there wasn't any, I just posted a game. Borislav Ivkov was certainly no patzer, he was an elite GM at the time.
I wasn't particularly recommending the KIA to anyone, and in fact I recommended not to make it one's only opening as some people do.

When Fischer faced 1.e4 d5, he almost always took the pawn rather than go in for the KIA.
Fischer consistently chose active play and when given the choice, played 1.e4 and 2.d4 far more often than he played 2.d3. Even in the Caro-Kann, he chose Nc3 rather than the KIA.
So the argument that the KIA must be good cos Fischer played it ignores the body of Fischer's work and the lines that he used the most.
Again, you are arguing with windmills. I didn't say that he used it against just anything, or that it was his main opening. If you looked at Fischer's games carefully, you would see exactly which lines he used the KIA against. (I am not going to volunteer this info.)
Dvoretsky says it is a good choice for an attacking repotear. Emms too, Jesper Hall. Bobby Fischer used it. Bologan, Morozovich, to mention two modern and very stong players.
But, then there are so many other players claiming that KIA is toothless. "It doesn't create any problems for Black". Watson, e.g., says Black can easily equalize.
How can this be?