Long diagonal in chess

Long diagonal

Definition

The long diagonal in chess refers to either of the board’s two longest diagonals: a1–h8 (dark-squared) and h1–a8 (light-squared). A bishop placed on one end of a long diagonal can “rake” across the entire board on that color, exerting long-range influence from one wing to the other. Because bishops move diagonally, the long diagonals are their natural highways, and control of these lines is a recurring theme in opening, middlegame, and endgame play.

How it is used in chess

Typical usage

Players often develop a bishop to a fianchetto square (b2 or g2 for White, b7 or g7 for Black) to control a long diagonal. This setup is central to many hypermodern systems where the center is controlled from a distance rather than immediately occupied with pawns.

• Fianchetto setups: White plays g3/Bg2 or b3/Bb2; Black plays ...g6/...Bg7 or ...b6/...Bb7. See Fianchetto and Double fianchetto.
• Pressure on the center: A bishop on g2 or g7 eyes the e4/e5 and d5/d4 squares, supporting pawn breaks and tactical themes.
• King safety and counterplay: In structures like the Dragon Variation or King\u0027s Indian Defense, the fianchettoed bishop defends the king while simultaneously pointing down the entire a1–h8 or h1–a8 diagonal for counterplay.
• Endgame reach: In bishop endgames, access to a long diagonal can decide races, restrain passed pawns, or create an impenetrable blockading setup (or a drawing Fortress).

Strategic and historical significance

Hypermodern revolution

In the early 20th century, hypermodern pioneers like Réti and Nimzowitsch championed controlling the center from afar. Their systems frequently place bishops on long diagonals (g2/b2 or g7/b7), delaying or even discouraging early pawn occupation of the center.

Why the long diagonal matters

• Space and scope: A bishop on a long diagonal influences both wings, creating latent threats and improving piece coordination.
• Targets and tactics: Long diagonals often host pins, skewers, and X-ray attacks against high-value targets on the same diagonal (king, queen, rooks).
• Pawn structure interplay: Pawns that open or block the long diagonal (e.g., c- or e-pawn pushes) can determine whether a bishop becomes a Good bishop or a Bad bishop.
• King safety: Moving the f-pawn early can expose the long diagonal to checks or sacrifices, a classic practical pitfall at all levels.

Tactical motifs on the long diagonal

Common patterns

• Pin and Skewer: A bishop on b2/g7 can pin a knight or skewer a rook/queen if the king lurks behind.
• Discovered attack and Clearance: Freeing the diagonal with a pawn or minor piece move can unleash a hidden bishop.
• X-ray pressure: Even if pieces block the line, the bishop’s latent power can tie down defenders and create Overworked pieces.
• Crossfire mates: Patterns like Boden\u0027s mate feature two bishops delivering mate on intersecting long diagonals.
• Raking shots: The so-called “Raking bishops” theme uses a long diagonal to sweep through multiple tactical points.
• Deflection/Decoy: The defender is lured off the diagonal, enabling tactics on key squares (e.g., h2/h7 or a2/a7).

Openings that spotlight the long diagonal

Representative systems

• Black: Dragon Variation (Sicilian) with ...g6 ...Bg7; King\u0027s Indian Defense; Gr\u00FCnfeld Defense; Pirc Defense and Modern Defense.
• White: English Opening with g3/Bg2; Reti-type fianchetto; Catalan-style setups with g3/Bg2.
• Dynamic gambits: Benko-style queenside pressure often cooperates with a bishop on b7 along h1–a8.

Examples

Example 1: Fianchetto control of a1–h8

After a standard King’s Indian Fianchetto move order, Black’s bishop on g7 rakes the a1–h8 diagonal, influencing the queenside and central dark squares:

1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. g3 O-O 5. Bg2 d6 6. Nf3

Notice how the g7–bishop eyes a1 and the e5/d4 squares, supporting ...e5 or ...c5 breaks while defending its king.

Interactive view:

Example 2: Dragon pressure on the long diagonal

In the Sicilian Dragon, Black’s Bg7 points down the long diagonal toward d4, b2, and h2, creating tactical resources against White’s center and king:

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 g6 6. Be3 Bg7 7. f3 O-O 8. Qd2 Nc6 9. O-O-O

Black often leverages the diagonal with moves like ...d5 or ...Be6–...Rc8–...Ne5, and tactical hits on d4/h2.

Interactive view:

Example 3: Boden’s Mate on crossing long diagonals

In the classic Boden’s Mate (Schulder–Boden, London 1853), two bishops coordinated on intersecting long diagonals to checkmate a king trapped on c8. The mating picture places White bishops on a3 and b2 (or analogous squares), with the king boxed by its own pieces on b7/d7. This illustrates how domination of both long diagonals can produce a sudden, elegant mate. See Boden\u0027s mate.

Practical tips

How to open or close the long diagonal

• Open it: Use pawn breaks like c4/c5 or e4/e5 (depending on color) to clear the line for your fianchettoed bishop.
• Close it: Advance a central pawn (e.g., e5 for White against a Bg7) to blunt the bishop; place a knight on d4/e5 or d5/e4 to block the diagonal.
• Prophylaxis: Avoid weakening moves (e.g., premature f-pawn pushes) that expose king-diagonal tactics.
• Coordination: Build a queen–bishop battery on the long diagonal when aiming for kingside attacks or pressure on a sensitive square like h7/h2. See Battery.

Common pitfalls

• Walking into a pin: A knight on f3/f6 can be pinned to the king/queen along the long diagonal.
• LPDO—Loose Pieces Drop Off: Unprotected pieces on the diagonal often fall to tactics.
• Trapping your own bishop: Pawn chains like e5–f4 (for White) or ...e4–...f5 (for Black) can imprison a fianchettoed bishop if timed incorrectly.

Endgames and the long diagonal

Long-range control in simplified positions

• Stopping passers: A bishop on the long diagonal can restrain a distant passed pawn, sometimes from across the board.
• Wrong-colored bishop trap: In rook-pawn endgames, the promotion square color matters; a “Wrong-colored bishop” cannot help, even with long-diagonal control.
• Opposite bishops: In Opposite bishops endings, the side with a more active bishop on a long diagonal often harasses pawns and creates drawing or winning chances with a far-reaching king–bishop battery.

Related concepts and see also

• Fianchetto, Double fianchetto, Good bishop, Bad bishop, Battery, Raking bishops
• Pin, Skewer, X-ray, Discovered attack, Clearance
• Dragon Variation, King\u0027s Indian Defense, Gr\u00FCnfeld Defense, English Opening

Fun facts and anecdotes

• The term “long diagonal” is universal among players and authors; it’s one of the first board-geography ideas taught after basic moves.
• Great attackers from the Romantic era to modern super GMs love fianchetto bishops for their dual role: king defenders and lethal snipers.
• Two bishops placed on both long diagonals can feel like a crossfire—one reason the Bishop pair is a long-term asset.
• Streamers sometimes dramatize a “laser” along the long diagonal when the bishop “beams” through multiple tactical points—watch for surprise tactics in time scrambles and don’t fall for a Cheap shot.

Want to test your long-diagonal instincts? Challenge a friend like k1ng and track improvement over time: .