Philidor Countergambit

The Philidor Countergambit is the move Philidor himself recommended against 3. d4. Black strikes at e4 at once instead of conceding the center with 3...exd4 or holding it with ...Nd7. The price is a loosened kingside and lagging development, and White has several good replies. Engines give White a large advantage, though in practice Black scores nearly as well as White. Morphy played it in 1858, and later Bronstein, Mestel, Kosten and Nakamura also tried it. Authorities have repeatedly dismissed it, yet it keeps returning to practice.

The most frequent reply is 4. dxe5 fxe4 5. Ng5 d5, when 6. e6 is the del Rio Attack, known since 1763, and 6...Bc5 7. Nc3 is the Berger Variation. Steinitz preferred the more positional 4. exf5, usually met by 4...e4 5. Ng5. The Zukertort Variation, 4. Nc3, sets a trap: 4...fxe4 5. Nxe4 d5 6. Nxe5 dxe4 7. Qh5+ g6 8. Nxg6 leaves Black in trouble. Engines rate 4. Bc4 highly, and some sources call it the clearest route to an advantage. After the recommended 4...Nc6, White continues 5. Ng5 Nh6 6. d5 and gains space in a fairly closed position.