What is castling?

Rules :: What is castling?

A "special" move was made in order to help the protection of the King.

Castling can only be made when:

• There are no pieces in between the Rook and the King.
• The King has not yet moved. 
• The Rook that is castling with the King has never moved. 
• The King is not in check 
• The King will NOT be crossing squares that are attacked by opponent's pieces.

Here are a few positions in which white can castle. These diagrams will show how castling works.

1. White can castle by moving his King two squares to the right (as indicated by the arrow).
   
       
   
   
2. White can castle by moving his King two squares to the left (as indicated by the arrow).
   
       
   
   
3. In this position, from a real game, white can castle by moving his King to the right by two squares.
   
       
   
   
4. Here, white cannot castle to the right (Kingside) because the black queen controls one square in the King's trajectory. However White can castle to the left (Queenside) because the queen covers no square in the King's trajectory.  Black, on the other hand, can castle to the left(Kingside) but not to the right (Queenside) as the white queen controls a square that the King would have to go through.
   
   
   
   
5. Here, white cannot castle to the right (Kingside) because his rook has already moved. He can, however, castle to the left (Queenside). Black, on the other hand, is in check by the Bishop. So he cannot castle at all this move.