Four Knights Game

Both sides bring out both knights — a symmetrical, solid opening that was very popular before the First World War.

It is reached after 6 moves: 1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6.

White is to move and has 29 legal moves. Over the next four moves — two for each side — the game can branch into 773,691 different games. Those games reach 269,353 different positions: most positions can be reached in more than one way, 2.9 on average.

The Lichess opening list names 45 further lines after this position, such as Spanish Variation (4. Bb5) and Scotch Variation (4. d4).

The same moves can be played in 36 different legal orders that all reach this position. For example 1. Nf3 e5 2. e4 Nc6 3. Nc3 Nf6, which starts as the Zukertort Opening.