How to Castle

King can't move through attack

You also can't castle if your King moves through a square that is under attack. In this diagram, the white Bishop is attacking the square to the left of the black King, so Black can't castle in that direction. Black can, of course, still castle to the right.

Index: How to Castle

1. The King's special move
2. King two squares toward the Rook which hops over the King
3. Castle to either side
4. King and Rook can't have already moved
5. King can't be under attack
6. King can't move through attack
7. King can't end under attack
8. No restrictions on Rooks regarding attacks