Anderssen's Opening

Adolf Anderssen played 1. a3 in his 1858 match against Paul Morphy. A waiting move: White keeps every option open and lets Black commit first.

It is reached after a single move: 1. a3.

Black is to move and has 20 legal moves. Over the next four moves — two for each side — the game can branch into 181,046 different games. Those games reach 66,799 different positions: most positions can be reached in more than one way, 2.7 on average.

The Lichess opening list names 4 further lines after this position, such as Polish Gambit (1... a5 2. b4) and Van Geet Opening, Battambang Variation (1... e5 2. Nc3).