Diagonal
A diagonal is the slanting path a bishop travels, a straight run of squares of a single color from one edge of the board to a neighboring edge, also used by the queen and by a pawn when it captures.
Every diagonal consists of squares of one color only. A bishop therefore stays on its diagonals and never leaves its color complex. The long diagonals, a1 to h8 and h1 to a8, are the longest with eight squares each, and they pass through the center.
Diagonals are central to strategy. A fianchettoed bishop on g2 or b2 aims down the long diagonal at the enemy king or queenside. Opening a diagonal toward the king, with a pawn exchange, is a normal way to start an attack. The queen also moves along diagonals, so a battery of queen and bishop on one diagonal is a classic attacking setup.
Pawns relate to diagonals too. A pawn captures one square diagonally forward, which is why pawn chains point along diagonals and why you attack a chain at its base.
Typical mistakes: ignoring a long diagonal that has quietly opened toward your king, or blocking your own bishop with pawns on its color. If the bishop is hemmed in by its own pawns, it becomes a bad bishop.
A tip for calculation: when you consider a move, trace the diagonals leaving its target square. Many tactics, such as skewers, pins and discovered attacks, run along a single diagonal that a quick look would have shown.
It sits close to Fianchetto. A fianchetto is the setup where a bishop sits on b2, g2, b7 or g7 behind a pawn that has moved one square, so that it eyes the long diagonal from a distance.
Knowing "Diagonal" is the easy part; what to practice next depends on your rating, and the improvement plans by rating band list the habits worth building at each level.
Related terms
The bishop moves any number of squares along a diagonal, as long as no piece stands in the way, so each bishop stays on one color of square for the entire game.
A fianchetto is the setup where a bishop sits on b2, g2, b7 or g7 behind a pawn that has moved one square, so that it eyes the long diagonal from a distance.
A battery is two of your pieces lined up on one file, rank or diagonal, with the rear piece backing up the front one so that both press on the same target.
A pin ties a piece to its square: a bishop, rook or queen attacks it, and stepping aside would expose a more valuable piece standing behind it on the same line.
A skewer attacks a valuable piece that stands in front of a less valuable one on the same line. The front piece must run, and the piece behind it is then taken.
A bad bishop is one whose own pawns stand mostly on its color, where they block its diagonals, leaving it with little range and few targets to attack.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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A game review, a read on your level and a written study plan from George Li.
Sources
- FIDE Laws of Chess (taking effect from 1 January 2023), Article 2.4, read Oct 21, 2026.
- FIDE Laws of Chess (taking effect from 1 January 2023), Articles 3.2 and 3.4, read Oct 21, 2026.
- FIDE Laws of Chess (taking effect from 1 January 2023), Article 3.7.3, read Oct 21, 2026.
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