When can you castle? is lesson 1 of 2 in Castling and en passant drills, a basics course suited to players rated around 400 (complete beginners). Castling moves the king to safety and brings a rook into play, both in one move. But there are rules. It has 4 interactive exercises: 3 find-the-move puzzles, 1 board-square exercise. You play every move on a board and get feedback straight away. The lesson is free.
What this lesson explains
To castle, the king moves two squares towards a rook, and the rook jumps over to the other side of the king. You may castle only if the king and that rook have never moved, the squares between them are empty, and the king is not in check. The king also may not cross or land on a square that an enemy piece attacks.
What you practise
When you castle on the king side, which squares must be safe from attack? Tap the square the king crosses and the square it lands on.
Castle. Only one side is allowed here. Which one, and why?
Black's bishop and rook aim at the squares next to your king. Castle on the side that is allowed.
You are in check from the bishop on b4, so you cannot castle right now. Get out of check in a way that keeps your right to castle.
Worked examples
When you castle on the king side, which squares must be safe from attack? Tap the square the king crosses and the square it lands on. Yes, f1 and g1. The rook itself may be attacked. Only the king's path must be safe.
Castle. Only one side is allowed here. Which one, and why? Right. Castling on the queen side is not allowed: the king would cross d1, which the rook on d8 attacks.
chessGM