The Castle Move or Castling

I.    Basic Description of The Castle Move or Castling

The King in combination with either of the player’s Rooks has an optional special move available called the castle move or castling. I will use the term “castling” in the rest of this lesson. This special move involves shielding the King on the back rank (1st rank for White, and 8th rank for Black) away from the center of the chessboard.

The Mechanics of Castling (section II below)
Reasons for Doing Castling (section III below)
Timing – General Considerations (section IV below)
To Which Side Should Castling Be Done? General Principles (section V below)
Is there some way to tell when to castle and not have it be detrimental? (section VI below)

II.    The Mechanics of Castling

       1.   How is Castling Done?

The King is moved two squares either to the right or left side along the back rank, and the Rook on that side is moved to the square in the same rank immediately adjacent to the square upon which the King lands and toward the center of the chessboard. The King may be castled to either the Kingside or the Queenside. In chess notation a Kingside castle is noted as 0-0 and a Queenside check is noted as 0-0-0.

Kingside castle: This involves moving the King two squares to the right to the King’s Knight square and the King’s Rook two squares to the left to the King’s Bishop square. The chess notation for a Kingside castle, 0-0, therefore is easily remembered and understandable.

Queenside castle: This involves moving the King two squares to the right to the Queen’s Bishop square and the Queen’s Rook three squares to the Queen’s square. The chess notation for a Queenside castle, 0-0-0, therefore also is easily remembered and understandable.

Castling with the Kings is shown in the below diagram.

DIAGRAM Castling-1:

       2.   When Can Castling Done? When Can Castling Not Be Done?

Each player may only castle once during a game, and only when

  • Both the King and Rook to be used in the castling have not moved; and
  • There are no intervening pieces (either the player’s or the opponent’s) located on the squares in the back rank between the King and Rook to be used in the castling; and
  • No opposing piece could check the King either on the square upon which the King would land after the castle move OR any of the intervening squares between the King and the Rook to be used in the castling (you should note that this naturally follows as a corollary or adjunct to the rule that the King may not move to a square upon which would the King would be in check); and
  • The King is not in check (the King may not castle to get out of check).

Castling cannot be done until at least one pawn advance has occurred and there has been development of two of a player’s pieces for a Kingside castle (Bishop and Knight on the Kingside) and three pieces for a Queenside castle (Queen, plus Bishop and Knight on the Queenside).

The earliest a Kingside castle may occur is on a player’s fourth move.

The earliest a Queenside castle may occur is on a player’s fifth move.

Another guiding principle is to develop Knights first and then the Bishops, but for castling a both a Bishop and a Knight need to be developed. Therefore, castling may occur perhaps out of necessity for “King Safety” before development of both Knights depending on the opening moves made by the players.

III.    Reasons for Doing Castling

1. Castling provides a defensive shield from the vulnerability of an opponent’s central attacks.

2. Castling frees up the Rook used in the castling toward the center of the chessboard for activity in open files and to be used to provide protection for the player’s central pawns.

3. Castling further usually connects up the two Rooks (unless one has already been lost to the opposing player), greatly enhancing their ability to attack and defend.

4. International Master Jeremy Silman, in his Chess Instruction for Beginners, King Safety, Part One, provides the following on castling:

“Why is it important to castle as quickly as possible?

The center is the most important part of the board (it’s FAR more important than the wings). If your opponent opens lines in that area, do you really want your King to take the brunt of his assault?

If your King is in the middle, your Rooks won’t be connected. Playing with one Rook against your opponent’s two is very poor math (in other words, castling gets your King to safety AND brings a Rook into play)!

Why attack when your own King is in the danger zone? It’s much better to get his Highness to a safe spot and only then start a battle. NEVER begin a fight if your King isn’t safe!

You can play on if you make a strategic mistake. You can play on if you hang a pawn. But if your King gets mated, the game is over. Simply put: winning a prolonged battle is MUCH easier if your King is safely castled.

It’s very hard to checkmate a castled King. You might be worried that your King will be executed in whatever corner it castled in, but it’s actually far simpler to torment a central King than a castled one.

Not castling doesn’t necessarily mean you’ll be mated. But it will make it harder for your forces to cooperate, and tactics based on the exposed King can easily lead to loss of material.”

IV.    Timing – General Considerations

Castling usually should be done no later than when the opposing player has developed pieces which may attack the King through the center files (d and e files, also called the King and Queen files).

If a player has castled, the opposing player should consider castling as soon as practicable because the opponent has freed up a Rook toward the center area of the chessboard for attacking along, and providing defensive control through, open lines and through the center. Therefore, “King Safety” dictates getting the opposing King also into a place of maximum protection away from the center of the chessboard as soon as possible.

V.    To Which Side Should Castling Be Done? General Principles

Typically, players will castle to the same side of the chessboard and most often Kingside castles are done.

Kingside castles generally provide the most protection for the King because it is ensconced centralized behind three pawns and provides protection for each of them. The King’s Knight may be positioned at f3 for White or f6 for Black (each square is said to be the most natural developed square for the King’s Knight) constructing a tightly compacted defensive fortress for a well-guarded and well-defended King.

Sometimes because of tactics, strategy, and positional reasons, the players will both castle to the Queenside. This is more rare.

In other cases, a player might do a Queenside castle and the opposing player does a Kingside castle, or vice-versa. These are more common than the dual Queenside castles, but less common than the dual Kingside castles.

In a Queenside castle there is a pawn usually left unprotected (the pawn at a2 for White and the pawn at a7 for Black).

The pawns at a2 and a7 in Queenside castles may be attacked and exploited as possible weaknesses in the defense around the shield afforded by castling to the Queenside, and provides an avenue into the players’ respective seventh and back ranks (for White-the 1st and 2nd ranks on the chessboard; for Black-the 7th and 8th ranks on the chessboard).

These pawns in Queenside castles are not easily defended, and therefore represent a drawback to doing Queenside castles as a normal rule.

A player needs to seriously consider the possible consequences of doing a Queenside castle, as indeed also a Kingside castle. However, the Queenside castle usually requires the player to do a more thorough and searching examination of the board, material advantage or disadvantage, positional structure, and pawn structure, before deciding to do a Queenside castle especially if a Kingside castle is still open and available to the player.

However, in some cases, a Kingside castle may no longer be an option because the King’s Rook has been moved or it is not an option at the time the player wishes to castle because the King is blocked from castling to the Kingside at that point (e.g., an opposing Bishop is attacking and controlling the f1 or g1 squares so that the White King cannot castle to the Kingside; or the f8 or g8 squares so that the Black King cannot castle to the Kingside). Therefore, a Queenside castle might be the only option available.

VI.    Is there some way to tell when to castle and not have it be detrimental?

Every player has gone through the bad experience of castling, following the above rules and principles, only to see their game plan become shattered, their King becomes very vulnerable, and under a relenting attack by the opponent. So, what happened? Isn’t castling supposed to be a good thing to do?

As with anything in chess, general rules and principles are just…well, plain and simply – general! So…yes, castling generally is a very good thing to do.

However, the timing, and which type of castling to do, greatly depends on the opening moves which are played by the players.

More specifically, when and what type of castling to be done depends on the offensive and defensive structures which have developed in the position on the board.

As you play games and work with castling and developing defensive positions, the timing and to which side you should castle will become more routine because you will gain experience in seeing how “vulnerabilities” dictate determining when and to which side you should castle. You must develop a sense and appreciation for the nature of vulnerabilities and attacking capabilities on the board to adequately execute castling to take the fullest advantage of the defensive power of castling.

Some things a player needs to consider:

  • Is it an open game? Are there are open files and maneuverability for pieces (especially the Bishops) through the center of the board?
  • Is it a closed game? Is the center blocked off by the pawn structure or positioning of pieces (especially a Knight centrally located (e.g., a White Knight at e5, or a Black Knight at e4), thereby limiting maneuverability of the Bishops. Closed games usually dictate more extensive use of the Knights.
  • Has the opponent “fianchettoed” – advanced the middle pawn of the three pawn defensive front in the normal castle position out one square and moved a Bishop to b2 or g2 for White, or b7 or g7 for Black, or done both, so that the Bishop has or may gain control of the long diagonal pointed at a King castled to the opposite side of the board?
  • Does the player intend to fianchetto, to one or both sides?
  • Is one or the other sides of the board significantly cramped or limited in space by the pawn structure and/or positioning of pieces on the board, which might dictate or force attacking maneuvers through the other side of the board.
  • Is the wing file on the side to which the player intends to castle (the h file for Kingside castles; and the a file for Queenside castles) already opened, or under a threat to be opened, or vulnerable to being opened?Think about:
    • Can the opposing player obtain a Bishop-Queen or Queen-Bishop battering ram aimed along the diagonal toward the defensive pawn positioned in the wing file
    • Is the King’s Knight in a Kingside castled developed to its most natural defensive square…f3 for White Kingside castling and f6 for Black Kingside castling, providing defense for the pawn in the wing file.

An open wing file against a castled King is extremely vulnerable for attacking and checkmating the castled King.