Sicilian Defense:Najdorf Variation

Named after Miguel Najdorf. 5...a6 may be the most famous move in modern opening theory; the Najdorf was the favourite weapon of Bobby Fischer and Garry Kasparov.

It is reached after 10 moves: 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6. It is a line of the Sicilian Defense.

White is to move and has 43 legal moves. Over the next four moves — two for each side — the game can branch into 1,591,216 different games. Those games reach 516,541 different positions: most positions can be reached in more than one way, 3.1 on average.

The Lichess opening list names 40 further lines after this position, such as English Attack (6. Be3) and Opocensky Variation (6. Be2).

The same moves can be played in 936 different legal orders that all reach this position. For example 1. Nf3 c5 2. e4 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6, which starts as the Zukertort Opening.