Rules and Basics
Castling
Definition
Castling is a special move where the king and rook move simultaneously in one tempo. Two types exist: kingside castle (short, notated O-O) and queenside castle (long, notated O-O-O). Castling is the primary way to secure the king plus activate the rook.
Usage and Example
Castling conditions: (1) king and rook have never moved, (2) squares between them are empty, (3) king is not currently in check, (4) squares the king traverses are not attacked by opponent pieces.
Grandmaster Tier Context
T1 Beginner. Introduced in sessions 3-5 after basics. Grandmaster coaches emphasize castling as a priority in the first 10-15 moves to secure the king before the middlegame.