Bishop's Opening

The Bishop's Opening develops the king's bishop at once, aiming at f7 and covering d5 so that Black cannot easily free the game with ...d5. Because the knight stays on g1, the f-pawn remains mobile, and a later f4 can steer the game into King's Gambit or Vienna territory. Unlike 2. Nf3, the move puts no pressure on e5, which gives Black a wide choice of replies. The same flexibility makes it a transpositional device: after 2...Nf6 White need not allow Petrov's Defense, which is why John Nunn adopted it and Peter Lékó used it against Vladimir Kramnik in the 2007 World Championship.

The Berlin Defense, 2...Nf6, attacks e4 at once. The usual answer is 3. d3, after which 3...c6, the Paulsen Defense, prepares ...d5 to build a center with gain of time against the bishop, typically 4. Nf3 d5 5. Bb3; this is the most important line that cannot arise from the Italian or the Vienna. After 3. d3 Nc6 4. Nc3 the Vienna Hybrid arises, where Black frequently plays 4...Na5 to acquire the bishop pair. Sharper alternatives on move three are the Ponziani Gambit 3. d4, usually leading to the Urusov Gambit after 3...exd4 4. Nf3, and 3. Nf3 Nxe4 4. Nc3, the Boden-Kieseritzky Gambit.

The Boi or Classical Variation, 2...Bc5, mirrors White's development. White may transpose with 3. Nc3 or 3. Nf3, or stay independent with 3. c3, the Philidor Variation, preparing d4; Black can answer that with the Lewis Countergambit 3...d5. The immediate 3. d4 is the Lewis Gambit, and 3. b4 produces Evans-like play. In the Lichess database 2...Nc6 is slightly more frequent than 2...Nf6; it leaves White to choose between the Italian with 3. Nf3 and the Vienna with 3. Nc3. Rarer tries include 2...c6, the Philidor Counterattack, the Khan Gambit 2...d5, and the Calabrese Countergambit 2...f5, which is regarded as unsound.

The opening was analyzed by Lucena and Ruy Lopez and later championed by Philidor, but lost ground once Black's defenses improved in the mid-19th century. Weaver Adams claimed it won by force, a view not borne out in practice; modern theory, including Modern Chess Openings, considers the position level with correct play, and the engine agrees. Bent Larsen revived it from the 1964 Interzonal onward, and Garry Kasparov has used it as an occasional surprise. It ranks among the most frequently reached named positions online.