Ruy Lopez:Exchange Variation

White gives up the bishop for the c6 knight and doubles Black’s pawns, aiming for a better endgame. Bobby Fischer revived it in the 1960s.

It is reached after 7 moves: 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6. It is a line of the Ruy Lopez.

Black is to move and has 26 legal moves. Over the next four moves — two for each side — the game can branch into 614,162 different games. Those games reach 216,169 different positions: most positions can be reached in more than one way, 2.8 on average.

The Lichess opening list names 10 further lines after this position, such as Normal Variation (4... dxc6 5. O-O) and Keres Variation (4... dxc6 5. Nc3).

The same moves can be played in 22 different legal orders that all reach this position. For example 1. Nf3 e5 2. e4 Nc6 3. Bb5 a6 4. Bxc6, which starts as the Zukertort Opening.