user3381: We all known that Bobby Fischer has published the famous "A Bust to The King's Gambit", where the gambit is said to be losing for white. Why is it so? Is there any line that can secure black an advantage in the opening, assuming best play from white from today's point of view?

user18367: Just my totally subjective opinion. Seems to me that at sub-master level - the goal is to have fun and enjoy the thrills and chills of the game.
So why not play King's Gambit as well as all the other gambits ?
Accept that you might get blasted off the board - but you might equally wind up getting some sudden inspiration and doing the same to your opponent.
Why even worry about whether or not grandmasters currently favor an opening or whether it is fashionable at the moment ?
And who cares if computers like a line or not ?
I love it when people throw gambits at me that I am totally unprepared for - it gets the juices flowing.

user2042: 
We all known that Bobby Fischer has published the famous "A Bust to The King's Gambit", where the gambit is said to be losing for white. Why is it so? Is there any line that can secure black an advantage in the opening, assuming best play from white?

It is not refuted but the Modern variation is very "pleasant" for Black at the moment, even though being "equal". The fact is that White barely holds equality here, and if he makes the slightest mistake then chances are high for him to lose the game. I am referring to the line 1.e4 e5 2.f4 exf4 3.Nf3 d5! 4.exd5.
Other old popular lines are very sharp and unexplored but mainly easier to play with Black. I refer to the lines where Black plays ...g5 with Black's dark squared bishop being posted on d6 or g7. These are simply ultra sharp, inhuman lines where even computers explode!
That is the reason why you will not see King's Gambit being played at the top/master level:

Too much memorization of lines which can be refuted by one computer-like novelty;
Even if White manages to get out of the opening with "equal" position, Black usually has easier time playing the middlegame;

I have checked the evaluations of all the lines in the Chess Informant ECO ( 2006 ) and my claims are supported -> White will always have a move that offers equal / sharp game, but the positions are wild and very hard to play.
This is not something that top GMs want, they do not enter into highly tactical lines. 
The reason for this is that in order to play this type of chess, you need to be physically very fit, you need to solve puzzles on a daily basis, you lose a lot of energy over the board when playing like this ( this is very dangerous for tournament play because you will play subsequent games worse ), the amount of stress you suffer is very high, and most of the time the entire line can be refuted by a single novelty found by a computer. Furthermore, the openings like this reduce to "I calculate better than you" type of game, so GM can not defeat markedly weaker player if he prepared his opening and calculates as good as that GM ( I have seen players who "fit this bill" so it is not impossible ).
If you intend to play King's Gambit as White, or you play 1...e5 by all means get John Shaw-King's Gambit ( 2013 ) as it is most up-to-date publication and the coverage is simply exceptional.
I wish I could give you some illustrative lines but the material is so vast that it would not fit in 10 posts or even more! Just get the book and all will be clear!
Best regards.

3381: <p>We all known that Bobby Fischer has published the famous &quot;<a href="http://brooklyn64.com/wp-content/uploads/2015/11/a-bust-to-the-kings-gambit.pdf" rel="nofollow noreferrer">A Bust to The King's Gambit</a>&quot;, where the gambit is said to be losing for white. Why is it so? Is there any line that can secure black an advantage in the opening, assuming best play from white from today's point of view?</p>
 18367: <p>Just my totally subjective opinion. Seems to me that at sub-master level - the goal is to have fun and enjoy the thrills and chills of the game.</p>

<p>So why not play King's Gambit as well as all the other gambits ?
Accept that you might get blasted off the board - but you might equally wind up getting some sudden inspiration and doing the same to your opponent.</p>

<p>Why even worry about whether or not grandmasters currently favor an opening or whether it is fashionable at the moment ?</p>

<p>And who cares if computers like a line or not ?</p>

<p>I love it when people throw gambits at me that I am totally unprepared for - it gets the juices flowing.</p>
 2042: <blockquote>
  <p>We all known that Bobby Fischer has published the famous "A Bust to The King's Gambit", where the gambit is said to be losing for white. Why is it so? Is there any line that can secure black an advantage in the opening, assuming best play from white?</p>
</blockquote>

<p>It is <strong>not</strong> refuted but the <em>Modern variation</em> is very "pleasant" for Black at the moment, even though being "equal". The fact is that White <strong>barely</strong> holds equality here, and if he makes the slightest mistake then chances are high for him to lose the game. I am referring to the line <code>1.e4 e5 2.f4 exf4 3.Nf3 d5! 4.exd5</code>.</p>

<p>Other old popular lines are very sharp and unexplored but <strong>mainly easier to play</strong> with Black. I refer to the lines where Black plays <code>...g5</code> with Black's dark squared bishop being posted on <code>d6</code> or <code>g7</code>. These are simply ultra sharp, inhuman lines where even computers explode!</p>

<p>That is the reason why you will not see King's Gambit being played at the top/master level:</p>

<ol>
<li><p>Too much memorization of lines which can be refuted by one computer-like novelty;</p></li>
<li><p>Even if White manages to get out of the opening with "equal" position, Black usually has easier time playing the middlegame;</p></li>
</ol>

<p>I have checked the evaluations of all the lines in the <em>Chess Informant ECO ( 2006 )</em> and my claims are supported -> White will <strong>always</strong> have a move that offers equal / sharp game, but the positions are wild and very hard to play.</p>

<p>This is not something that top GMs want, they do not enter into highly tactical lines. </p>

<p>The reason for this is that in order to play this type of chess, you need to be physically very fit, you need to solve puzzles on a daily basis, <strong>you lose a lot of energy over the board</strong> when playing like this ( this is very dangerous for tournament play because <strong>you will play subsequent games worse</strong> ), the amount of stress you suffer is very high, and most of the time the <strong>entire line</strong> can be refuted by a single novelty found by a computer. Furthermore, the openings like this reduce to "I calculate better than you" type of game, so GM can not defeat markedly weaker player if he prepared his opening and calculates as good as that GM ( I have seen players who "fit this bill" so it is not impossible ).</p>

<p>If you intend to play King's Gambit as White, or you play <code>1...e5</code> <strong>by all means</strong> get <em>John Shaw-King's Gambit ( 2013 )</em> as it is most up-to-date publication and the coverage is simply exceptional.</p>

<p>I wish I could give you some illustrative lines but the material is so vast that it would not fit in 10 posts or even more! Just get the book and all will be clear!</p>

<p>Best regards.</p>
