Double pawn push

On its first move, a pawn may advance one square or make a double pawn push two squares forward on the same vertical line. Both the intermediate square and the destination must be empty. The pawn does not jump over a piece.

The option exists only from the pawn’s original square: White’s pawns begin on the second horizontal row and Black’s on the seventh. Because pawns never move backward, a pawn that has already moved cannot regain this option.

A double push may create an en passant right for an adjacent enemy pawn. On the immediate reply, that pawn may capture it as though it had advanced only one square. This special capture disappears if it is not used at once. Any pawn move also restarts the count under the rule that allows a draw claim after fifty moves by each player without a pawn move or capture. It is therefore an irreversible move in that sense: moving pieces back does not restore the earlier count.