An underestimated opening... Standard Chess

Anderssen's Opening is a chess opening defined by the opening move

1. a3.
It is named after unoffical World Chess Champion Adolf Anderssen, who played it three times[1][2][3] in his 1858 match against Paul Morphy.

This opening move does little for development or control of the center. In some cases, White can transpose the game to an opening where 1.a3 might have been useful, but using a tempo on such a move already on move one seems premature. As Anderssen's Opening is not commonly played, it is considered an irregular opening. The move is classified under the A00 code in the Encyclopaedia of Chess Openings.

Anderssen's Opening is not a very constructive move for White, more a waiting move. However, some players may enjoy the psychological value of such a move, or believe it will help them against an opponent with a superior knowledge of opening theory.