Wrong Diagonal Bishop  The Wrong Diagonal Bishop or Parallel-Diagonal Bishop (筋違い角 or 筋違角 "sujichigai kaku") is a shogi opening characterized by a bishop trade followed by dropping the bishop in hand on the 45 square if played by Black or the 65 square if played by White. The Wrong Diagonal Bishop opening is one of the oldest shogi openings appearing around the same time as the Black's Static Rook vs White's Traditional Ranging Rook type of openings (thus predating other old openings such as Fortress, etc). The Wrong Diagonal Bishop frequently appears in the recorded handicap games from the Edo period. The name comes from the bishop being only able to move to squares that are not available from the bishop's start position – thus, the "wrong diagonal." The main point of dropping the bishop is to fork two opponent pawns. Since the opponent is most likely to defend the pawn in their camp, the player can get a material advantage of one pawn. Furthermore, adopting such an early attack can put pressure on their opponent and disturb their normal development in other openings. After the bishop drop and pawn capture, the player must then contend with whether they will retreat their bishop to the left or right side. There are two main types of Wrong Diagonal Bishop openings. One variation stems from the Bishop Exchange opening, which is a Double Static Rook opening where both players advance their rook pawns and develop their left silvers to prevent each other from trading off their rook pawns. Here the Wrong Diagonal Bishop drop occurs immediately after the bishop trade off. The other variation – Primitive Wrong Diagonal Bishop (原始筋違い角) – has a very early bishop trade off and subsequent bishop drop. This occurs directly after the players' bishop diagonals are opened after the third move (or the fourth move if played by White). This set of variations leads to more unusual formations in which either player could play alternately a Static Rook or Ranging Rook position. Unlike the first Bishop Exchange variation, this Primitive variation has Black losing tempo. One of the aims of Primitive Wrong Diagonal Bishop as played by Black is to make it difficult for White to play a standard Ranging Rook strategy as in order to do White's rook must be moved twice (first to the sixth file, then to the fourth file) losing tempo. Otherwise, a Ranging Rook player must spend several moves developing their generals in order to keep their line of pawns defended while also clearing a path on rank 2 for the rook to be swung over to a Ranging Rook file.