Editing Castling (section)

===Strategy===
{{Chess diagram
| tright
|
|rd|  |  |qd|  |rd|kd|  
|pd|pd|  |bd|pd|pd|bd|pd
|  |  |nd|pd|  |nd|pd|  
|  |  |  |  |  |  |  |  
|  |  |bl|nl|pl|  |  |  
|  |  |nl|  |bl|pl|  |  
|pl|pl|pl|ql|  |  |pl|pl
|  |  |kl|rl|  |  |  |rl
| Position after 10.0-0-0: Opposite castling in the Yugoslav Attack
}}
Castling is generally an important goal in the [[Chess opening|opening]]: it moves the king to safety away from the {{chessgloss|center files}} of the board, and it moves the rook to a more active position (the f-file if castling kingside; the d-file if castling queenside).

The choice regarding to which side one castles often hinges on an assessment of the trade-off between king safety and activity of the rook. Kingside castling is generally slightly safer because the king ends up closer to the edge of the board and can usually defend all of the pawns on the castled side. In queenside castling, the king is placed closer to the center and does not defend the pawn on the a-{{chessgloss|file}}; for these reasons, the king is often subsequently moved to the b-file. In addition, queenside castling is initially obstructed by more pieces than kingside castling, thus taking longer to set up than kingside castling. On the other hand, queenside castling places the rook more efficiently on the central d-file, where it is often immediately active; meanwhile, with kingside castling, a [[Tempo (chess)|tempo]] may be required to move the rook to a more effective square.

Players may forgo castling for various reasons. In positions where the opponent cannot organize an attack against a centralized king, castling may be unnecessary or even detrimental. In addition, in certain situations, a rook can be more active near the edges of the board than in the center; for example, if it is able to fight for control of an open or semi-open file.

Kingside castling occurs more frequently than queenside castling. It is common for both players to castle kingside, less common for one player to castle kingside and the other queenside, and uncommon for both players to castle queenside. If one player castles kingside and the other queenside, it is called ''opposite castling'' or ''opposite-side castling''. Castling on opposite sides usually results in a fierce fight, as each player's pawns are free to advance to attack the opponent's castled position without exposing the player's own castled king. Opposite castling is a common feature of many openings, such as the [[Sicilian Defence, Dragon Variation, Yugoslav Attack, 9.Bc4|Yugoslav Attack]].