6...Bb4, or 6...Be6. Then 7.Bxe6 fxe6 his position remains a hard nut to crack." Philidor Countergambit: 3...f5 A more aggressive approach for Black after 3.d4 is 3...f5 (diagram), Philidor's original intention and recommendation. In the 19th century, 3...f5 was also played by Paul Morphy. The move can lead to more than the other lines, but is often considered dubious. Others maintain that 3...f5 is a valid idea. GM Tony Kosten considers the move respectable in his monograph on the opening. The move was also played by David Bronstein and by Teimour Radjabov. After 3...f5 White has several ways to proceed: 4.Nc3 (the Zukertort Variation) and White obtains a clear advantage: 4...fxe4 5.Nxe4 d5 (if 5...Nf6 6.Nxf6 gxf6 7.dxe5 fxe5 8.Bc4 Qf6 9.Ng5 Polugaevsky) 6.Nxe5 dxe4 7.Qh5+ g6 8.Nxg6 Nf6 (if 8...hxg6 9.Qxh8 Be6 10.Qe5+/− Larsen) 9.Qe5+ Kf7 (if 9...Be7 10.Nxh8 Nc6 11.Bb5 Qd5 12.Bg5+/− Zukertort) 10.Bc4+ Kg7 11.Bh6+ Kxh6 12.Nxh8 Bb4+ 13.c3 Qxh8 14.cxb4+/− (Keres). 4...exd4 5.Qxd4 fxe4 (if 5...Nf6 6.e5!) 6.Bg5 Nf6 7.Nxe4 Be7 8.Bc4 Nc6 9.Qe3+/− (Sozin). 4...Nf6 5.dxe5 Nxe4 6.Nxe4 fxe4 7.Ng5 d5 8.e6 Bc5 9.Nxe4!+/− (Sozin, Sokolsky). 4.Bc4 leads to clear advantage for White: 4...exd4 5.Ng5 Nh6 6.0-0 (6.Nxh7, the Jaenisch Variation, leads to an position after 6...Ng4! 7.Nxf8 Kxf8 8.Qxd4 Nc6) 6...Nc6 7.Re1 f4 (or 7...fxe4 8.Nxe4 Ne5 9.Bxh6 gxh6 10.f4 Nxc4 11.Nxd6+ +/−) 8.Bxf4 Qf6 9.Qd2 Ne5 10.Be2 Bg4 11.f3 Bd7 12.Bg3 0-0-0 13.f4+/−. 4...Nf6 5.Ng5 Qe7 (or 5...d5 6.dxe5 dxc4 7.Qxd8+ Kxd8 8.exf6+/−) 6.Bf7+ Kd8 7.Bb3 exd4 8.0-0+/− (Berger). 4...fxe4 5.Nxe5 d5 6.Qh5+ g6 7.Nxg6 Nf6 8.Qe5+ Be7 and continuing either 9.Qxe7+, 9.Nxh8 (Steinitz), or 9.Bb5+ (Keres). 4.dxe5 forces Black to complicate matters further with 4...fxe4 5.Ng5 d5 with an unclear position. After 6.e6 (the del Rio Attack), White obtains the upper hand after 6...Bc5 7.Nc3 (the Berger Variation), or 6...Nh6 7.Nc3! (Berger); however, Black can maintain lack of clarity with 6...Nf6!? 7.Nf7 Qe7 8.Nxh8 Bxe6, or 6...Bb4+ 7.c3 Bc5 8.Nf7 Qf6 9.Be3 Bxe6 10.Nxh8 Bxe3 11.fxe3 Qh4+ 12.g3 Qh6 13.Qd2 Nd7 14.c4 Ne5 15.Be2 dxc4 16.Nc3 Nd3+ 17.Bxd3 exd3 (Makarov). White also has 6.Nc3!? (Steinitz) and 6.c4. 4.exf5 e4 5.Ng5 Bxf5 6.Nc3 and White has a slight plus after 6...Nf6 7.f3 (Sozin), or 6...d5 7.f3. 3...Bg4?! Inferior is 3...Bg4, in light of 4.dxe5 Bxf3 (Black cannot recapture since 4...dxe5 5.Qxd8+ Kxd8 6.Nxe5 wins a clean pawn; or, Black can gambit a pawn with 4...Nd7, the Albin Variation) 5.Qxf3 (or White can obtain