3...exd4 4.Qxd4 Nc6 (Center Game, by transposition) 3...exd4 4.Nf3 (Urusov Gambit) 4...Bc5 5.0-0 Nc6 (Max Lange Attack, by transposition) 4...Nc6 (Two Knights Defense, by transposition) 4...Nxe4 5.Qxd4 (Urusov Gambit Accepted) 3.Nf3 (Petrov's Defense, by transposition) 3...Nxe4 4.Nc3 (Boden–Kieseritzky Gambit) 3.f4 (Greco Gambit) 3...Nxe4 4.d3 Nd6 5.Bb3 Nc6 or 5...e4 3...exf4 (King's Gambit, by transposition) Classical Defense: 2...Bc5 The Classical Defense is Black's symmetrical response, 2...Bc5. White can then transpose into the Vienna Game (3.Nc3) or the Giuoco Piano (3.Nf3 Nc6), or remain in the Bishop's Opening with the Wing Gambit (3.b4) or the Philidor Variation (3.c3). The main line of the Philidor Variation runs: 3.c3 Nf6 4.d4 exd4 5.e5 d5! 6.exf6 dxc4 7.Qh5 0-0 8.Qxc5 Re8+ 9.Ne2 d3 10.Be3. Transpositions into the King's Gambit Declined and the Giuoco Piano are also possible after 3.d3. The Wing Gambit results in positions similar to those in the Evans Gambit. It can transpose into the Evans Gambit, for instance by 3.b4 Bxb4 4.c3 Ba5 5.Nf3 Nc6. Black's most energetic response to the Philidor Variation is the Lewis Countergambit, 3.c3 d5, named for the English player and author William Lewis (1787–1870) who published analysis of the line in 1834. Among amateurs, 3.Qf3 and 3.Qh5 are also popular, threatening an immediate Scholar's mate. But the threat is easily met (e.g. 3.Qh5 Qe7) and the moves are considered inferior since they hamper White's development or leave the queen exposed, leading to loss of tempo. Summary after 2...Bc5 3.b4 (Wing Gambit) 3.c3 (Philidor Variation) 3...d5 (Lewis Countergambit) 3...d6 3...Nf6 3.Nc3 (Vienna Game, by transposition) 3.d3 3.Nf3 Nc6 (Giuoco Piano, by transposition) 3.Qg4 Other Black responses Other Black second moves are rarely played. If Black tries to transpose into the Hungarian Defense with 2...Be7?, then 3.Qh5 wins a pawn. The Calabrese Countergambit (2...f5) is named after Greco's homeland, Calabria. It is considered dubious, as the line recommended by Carl Jaenisch, 3.d3 Nf6 4.f4 d6 5.Nf3, gives White the advantage. Other analyses, however, have found that the sharp 3.f4! or safe 3.Nc3 are better for White than 3.d3. Summary of other Black responses 2...c6 (Philidor Counterattack) 2...Nc6 2...d6 2...f5?! (Calabrese Countergambit) 3.d3 (Jaenisch Variation) References Bibliography Adams, Weaver W. (1939). White to Play and Win. . External links Goeller, Michael. The Bishop's Opening. Harding, Tim (August 1998). The Kibitzer: What Exactly is the Bishop's Opening?. ChessCafe.com. Harding, Tim (September 1998). The Kibitzer: The Eternal Appeal Of The Urusov Gambit.