The Complete Chess Course From Beginning To Winning Chess! (2016)
The Basic Rules of Chess
We have seen what happens when the king is exposed to attack. The special move known as “castling” offers a valuable method for safeguarding the king against attack.
Castling is the only move in chess which is really two separate moves - a king move and a rook move. Castling, as well, is the only move that each player can carry out only once during a game.
It is possible to castle with the king and king rook (kingside castling) or with the king and queen rook (queenside castling). Diagrams 33 and 34 show how kingside castling is accomplished. (D)
Before kingside castling (king and king rook)
After kingside castling
To castle kingside, a player moves his king two squares, landing next to the king rook.
He then moves his rook to the other side of the king. When castling is completed, the castled king and rook are on adjacent squares, as in Diagram 34.
Queenside castling is illustrated in Diagrams 35 and 36. (D)
Before queenside castling
(king and queen rook)
After queenside castling
Requirements for Castling
Castling is permanently impossible if:
(1) The king has already moved (Diagram 37) or;
(2) The rook intended for castling has already moved (Diagram 38). (D)
Black cannot now castle because his king has moved from its original square.
White can castle kingside. (His king rook is still on its original square and has not moved.)
When Castling is Impossible
Castling is impossible when:
(1) The squares between the king and rook are not all vacant (Diagram 39).
(2) A player’s king is in check (Diagram 40).
(3) The king has to pass over a square commanded by an enemy unit (Diagram 41).
(4) The king will land on a square commanded by an enemy unit (Diagram 42).
While castling is impossible as long as any of these conditions apply, castling becomes feasible as soon as all limiting conditions are removed. (D)
White cannot castle because one of the squares between his king and king rook is still occupied.
White cannot castle because his king is at the moment being checked by the black bishop.
Black cannot castle because in order to do so his king would have to pass over a square controlled by White’s dark-square bishop.
White cannot castle because the square on which his king would land is controlled by Black’s dark-square bishop.