Opposite-coloured bishops
Opposite-coloured bishops
Definition
“Opposite-coloured bishops” (often abbreviated “OCBs”) is the term used when each side has a single bishop and the bishops patrol squares of different colours—one controls the light squares, the other the dark. The most common material balance is light-squared bishop vs. dark-squared bishop, but the idea also appears in positions with additional pieces (rooks, queens, pawns) still on the board.
How it arises
- Early trades in symmetrical openings (e.g., 1. d4 d5 2. Bf4 Bf5 3. e3 e6 4. Bd3 Bxd3 5. Qxd3 followed by …Bxd3).
- Middle-game exchanges in which each player captures the enemy bishop that sits on the same colour complex.
- Endgame “purification” in which minor pieces are swapped, deliberately steering into a theoretically drawn OCB ending.
Strategic significance
Opposite-coloured bishops carry a dual reputation:
- Endgames = Drawish. With only rooks or no heavy pieces left, one side can plant its pawns on the opposite colour of the enemy bishop and build an almost impregnable fortress. Roughly half a pawn of advantage is usually not enough to win.
- Middlegames = Tactical fireworks. When queens are still present, the bishops act like non-interfering snipers. The attacker can overload the square complex his own bishop controls because the defender’s bishop simply cannot help there.
Typical plans
- Attacking side
- Place pawns on the same colour as the enemy bishop to restrict it.
- Open files toward the opponent’s king, often sacrificing a pawn.
- Create an “anchor” square (e.g., a protected knight on f6 vs. …Bg7).
- Defending side
- Trade queens or a pair of rooks to head for the drawish ending.
- Blockade opposite-coloured weak squares with the king.
- Keep pawns on the opposite colour of one’s own bishop to maximise its scope.
Historical perspective
The drawish nature of OCB endings influenced match strategy long before the computer era. In the 1921 World Championship, José Raúl Capablanca used a small, stable advantage plus opposite-coloured bishops to squeeze Emanuel Lasker in several games, wearing him down over the long match. Decades later, Anatoly Karpov refined the concept, deliberately steering into OCB endings a pawn up because he understood exactly which positions were still winning.
Illustrative examples
1. Drawing fortress: Korchnoi – Karpov, World Championship 1978 (Game 4)
Material: White Bc4, Re1, Qe2, pawns h4, g2, f3, e4, d3 vs. Black Bd4, Rf8, Qg7, pawns h6, g6, f7, e5, d6.
Despite an extra pawn, Korchnoi could not penetrate because Karpov’s dark-squared bishop glued everything together on the black squares.
2. Attack with OCBs: Tal – Gligorić, Bled 1961
Tal sacrificed a pawn to tear open the light squares around the black king
(g7-h6-f6) knowing Gligorić’s bishop was a bystander on the dark diagonal.
The game ended in a spectacular mating net starting with 24. Bxg7!!.
Common motifs & pitfalls
- Wrong-rook pawn: In King+Bishop+rook pawn vs. King, if the promotion square is the wrong colour, the defender draws by occupying the corner.
- Blockade breaks: Rook lifts and pawn breaks (f5 or h5) are often the only way to shatter a fortress, echoing famous attempts by Garry Kasparov against Veselin Topalov (Linares 1999).
- Lifelong diagonal: Remember that a bishop can never leave its colour complex; losing the “good” diagonal usually means you’ll never get it back.
Interesting facts & anecdotes
- Engines rate many OCB endgames at 0.00 from the outset, yet human champions (Capablanca, Karpov, Carlsen) kept winning them, proving that subtle technique can bend, though not break, the rules of thumb.
- Mikhail Tal once joked, “With opposite-coloured bishops, the board is split into two countries. I simply declare war only in mine.”
- The famous Kasparov – Deep Blue 1997 Game 1 featured an OCB middlegame where Kasparov’s light-square dominance outbalanced a pawn deficit and led to victory, showcasing the attacking side of the coin.
Key takeaways
- Opposite-coloured bishops favour the defender in simplified endgames.
- They favour the attacker in complex middlegames, especially with queens on the board.
- Understanding pawn structure colours (what squares your pawns sit on) is the single most important skill when playing OCB positions.