user5784: Suppose, you play a normal chess game, with the only exception that the opponent
 is not allowed to castle, but you are.
Do you have a decisive advantage ?

user4354: Castling is an important move that allows a player to put his king into the corner's safety. The rearrangement that occurs when a player castles is beneficial because the king usually finds increased safety, away from the dangerous centre files while the rook boosts its attacking potential by moving out of the corner. To explain how much of an advantage it gives to have your opponent not being able to castle, I will talk about some positional strategies that we can adopt to exploit the disadvantage of it.
Every player likes to control the centre, the strategy of central control is why you want your d and e pawns to come up to d3, e3, d4 and e4 squares and try and control d4 d5 e4 and e5 centre squares. This opens up the centre and if the king is unable to castle and go behind g or c pawn, this leaves him right behind the open pawn structure in the centre, while his opponent's king looks very safe behind the f g and h pawns.
So assume white is the one who is not allowed to castle, and black already has. White needs to think about counter attack on f, g and h files and wants to open the black king to create an attack, meanwhile his own king is already open while trying to control the centre by pushing his centre pawns. So here black gains the advantage of having more opportunities to create threats on the open white king and white now has to defend his own king and also think about creating access to black's king, so obviously white is in a much more difficult situation than Black. This is a great advantage that black gets off his opponent not being able to castle (and the reason why most openings include castling in it's book moves).
This can also be related to opposite side castling, where both sides are pushing their opposite pawns forward hoping to be the first to launch an attack (the Sicilian defence is one of the best example where this usually happens). After opposite side castling, both sides can also have their pawns in centre and fight for centre control. While the most important thing is that both can achieve equality in the center, they still don't have to worry about their king because if one player tries to start an attack on his opponent's king side, the other can start a counter attack. Consider the same situation in a position where white's king can not castle and is in e1, say whites pawns are on c2 d2 e3 and f2 protecting the king while the g and h pawns are marching forward to attack black's king. To achieve a successful attack white needs his major pieces to also support the g and h pawns, so not only most of white's pieces have to leave one corner of the board and come to the other, but white also has to give up the centre squares while supporting the corner. Meanwhile, black's minor and major pieces, which have access to the centre, help not only to attack white's King which is in e1, but can also defend his own king since the pieces which are in centre have more mobility and control many more squares than the ones that are in corner!
With proper play from the opening, a side which can castle will have the decisive advantage of an early attack on the opponents king.
However, there are a few instances where castling should be avoided. Some common reasons include:

If castling will expose your king to greater danger.
If your opponent’s most threatening pieces (especially the queen) have already left the board.
If your rook is supporting an important advance of a flank pawn.
If you have powerful tactics available immediately and castling will cost you the initiative.


user9419: In fact, Larry Kaufman (Komodo) did computer testing on this with Komodo, and found that White has about 50% winning chances when Black starts with no castling privileges. So it's a toss-up.
http://talkchess.com/forum/viewtopic.php?p=650339#650339

Here is a perfect example: In the initial position, forbid Black from
  castling. Komodo gives that position a score that is around where I
  think the dividing line between win and draw lies. I had Komodo 9.3
  play it out on four threads (to insure variety due to MP
  unpredictability) a hundred times at game in one minute. getting 49
  White wins, 46 draws, 5 Black wins. Then at two minutes plus one
  second, a similar result: 49 White wins, 49 draws, 2 Black wins. So
  just forbidding castling for Black appears to put the game right on
  the win/draw line. Of course results could be different at TCEC time
  controls on many cores, but it's not obvious whether the White win
  percentage would go up or down.

There have been some who have dubbed this "Kaufman chess", and suggested it as a sort of long-time control Armageddon method (rather than two rapid games, then two faster games, then two blitz games, and finally a blitz Armageddon, as in the FIDE World Cup).

5784: <p>Suppose, you play a normal chess game, with the only exception that the opponent
 is not allowed to castle, but you are.</p>

<p>Do you have a decisive advantage ?</p>
 4354: <p>Castling is an important move that allows a player to put his king into the corner's safety. The rearrangement that occurs when a player castles is beneficial because the king usually finds increased safety, away from the dangerous centre files while the rook boosts its attacking potential by moving out of the corner. To explain how much of an advantage it gives to have your opponent not being able to castle, I will talk about some positional strategies that we can adopt to exploit the disadvantage of it.</p>

<p>Every player likes to control the centre, the strategy of central control is why you want your d and e pawns to come up to d3, e3, d4 and e4 squares and try and control d4 d5 e4 and e5 centre squares. This opens up the centre and if the king is unable to castle and go behind g or c pawn, this leaves him right behind the open pawn structure in the centre, while his opponent's king looks very safe behind the f g and h pawns.</p>

<p>So assume white is the one who is not allowed to castle, and black already has. White needs to think about counter attack on f, g and h files and wants to open the black king to create an attack, meanwhile his own king is already open while trying to control the centre by pushing his centre pawns. So here black gains the advantage of having more opportunities to create threats on the open white king and white now has to defend his own king and also think about creating access to black's king, so obviously white is in a much more difficult situation than Black. This is a great advantage that black gets off his opponent not being able to castle (and the reason why most openings include castling in it's book moves).</p>

<p>This can also be related to opposite side castling, where both sides are pushing their opposite pawns forward hoping to be the first to launch an attack (the Sicilian defence is one of the best example where this usually happens). After opposite side castling, both sides can also have their pawns in centre and fight for centre control. While the most important thing is that both can achieve equality in the center, they still don't have to worry about their king because if one player tries to start an attack on his opponent's king side, the other can start a counter attack. Consider the same situation in a position where white's king can not castle and is in e1, say whites pawns are on c2 d2 e3 and f2 protecting the king while the g and h pawns are marching forward to attack black's king. To achieve a successful attack white needs his major pieces to also support the g and h pawns, so not only most of white's pieces have to leave one corner of the board and come to the other, but white also has to give up the centre squares while supporting the corner. Meanwhile, black's minor and major pieces, which have access to the centre, help not only to attack white's King which is in e1, but can also defend his own king since the pieces which are in centre have more mobility and control many more squares than the ones that are in corner!</p>

<p>With proper play from the opening, a side which can castle will have the decisive advantage of an <strong>early attack on the opponents king.</strong></p>

<p>However, there are a few instances where castling should be avoided. Some common reasons include:</p>

<ol>
<li>If castling will expose your king to greater danger.</li>
<li>If your opponent’s most threatening pieces (especially the queen) have already left the board.</li>
<li>If your rook is supporting an important advance of a flank pawn.</li>
<li>If you have powerful tactics available immediately and castling will cost you the initiative.</li>
</ol>
 9419: <p>In fact, Larry Kaufman (Komodo) did computer testing on this with Komodo, and found that White has about 50% winning chances when Black starts with no castling privileges. So it's a toss-up.</p>

<p><a href="http://talkchess.com/forum/viewtopic.php?p=650339#650339" rel="noreferrer">http://talkchess.com/forum/viewtopic.php?p=650339#650339</a></p>

<blockquote>
  <p>Here is a perfect example: In the initial position, forbid Black from
  castling. Komodo gives that position a score that is around where I
  think the dividing line between win and draw lies. I had Komodo 9.3
  play it out on four threads (to insure variety due to MP
  unpredictability) a hundred times at game in one minute. getting 49
  White wins, 46 draws, 5 Black wins. Then at two minutes plus one
  second, a similar result: 49 White wins, 49 draws, 2 Black wins. So
  just forbidding castling for Black appears to put the game right on
  the win/draw line. Of course results could be different at TCEC time
  controls on many cores, but it's not obvious whether the White win
  percentage would go up or down.</p>
</blockquote>

<p>There have been some who have dubbed this "Kaufman chess", and suggested it as a sort of long-time control Armageddon method (rather than two rapid games, then two faster games, then two blitz games, and finally a blitz Armageddon, as in the FIDE World Cup).</p>
