The promotion zone is the 'enemy camp', the farthest three ranks of the board, which are mostly occupied by the opposing player's pieces when the board is first set up. When a promotable piece enters the promotion zone, it has the option of "promoting" to a more powerful rank. Promotion is effected by turning the piece over after it moves, revealing the name of its promoted rank. The characters inscribed on the backs of the pieces to indicate promoted rank may be in red ink. Promotion is not mandatory if the unpromoted piece could move further on a later turn, and in some cases it may be beneficial to leave the piece unpromoted; however, there may be restrictions on whether the piece can promote again later. (The rule in the later chu shogi would always allow promotion on captures that touch the promotion zone, but would only allow promotion on a non-capture if the piece exited the promotion zone and then reentered.) Promotion is permanent and promoted pieces may not revert to their original rank.