Philidor Defense:Lion Variation

It is reached after 8 moves: 1. e4 e5 2. Nf3 d6 3. d4 Nf6 4. Nc3 Nbd7. It is a line of the Philidor Defense.

White is to move and has 37 legal moves. Over the next four moves — two for each side — the game can branch into 939,223 different games. Those games reach 320,627 different positions: most positions can be reached in more than one way, 2.9 on average.

The Lichess opening list names 8 further lines after this position, such as Nimzowitsch, Larobok Variation (5. Bc4 Be7 6. Ng5 O-O 7. Bxf7+) and Shirov Gambit (5. g4).

The same moves can be played in 288 different legal orders that all reach this position. For example 1. Nf3 e5 2. e4 d6 3. d4 Nf6 4. Nc3 Nbd7, which starts as the Zukertort Opening.