White moves its pawn two squares forward, setting up the en passant opportunity.

En passant is a special pawn capture that can occur immediately after a pawn moves two squares forward from its starting position and an enemy pawn could have captured it had it moved only one square forward.

The en passant capture must be performed on the very next turn, or the right to do so is lost. This rule was introduced in the 15th century to counteract the then-new rule that allowed pawns to move two squares on their first move.

Key points about en passant:

• It can only be performed by a pawn
• It can only occur immediately after a pawn moves two squares
• The capturing pawn must be on its fifth rank
• The captured pawn is removed from the board as if it had only moved one square