Anderssen's Opening

Anderssen's Opening, 1. a3, is classified under A00 in the Encyclopaedia of Chess Openings. It takes its name from Adolf Anderssen, who chose it three times with White in his 1858 match against Paul Morphy and scored 1½/3 with it, losing the first game, drawing the second and winning the third, although he lost the match. The move neither develops a piece nor contests the center. It is a prophylactic tempo: White in effect adopts Black's role with a3 already played, covering b4 and preparing b4, and steers toward lines where that extra move proves useful.

The most common reply is 1...e5. White can answer 2. c4, reaching an English or Reversed Sicilian structure (the same position as 1. c4 e5 2. a3) in which a3 supports b4 and resembles a Najdorf or Kan setup with colors reversed; all three Morphy games followed this path. Another route is 2. e4 Nf6 3. Nc3, transposing to Mengarini's Opening, where 3...Bc5 4. Nf3 yields a Two Knights structure with a3 inserted. The second most popular reply, 1...d5, stakes a direct central claim and tends to lead to Polish Opening positions if White plays b4, or a reversed Pirc after d3 and g3. Other options include 1...e6, 1...c5 (an a3 Sicilian, or a target for b4), and 1...g6, which occupies the long diagonal with Bg7 before White can set up b4 and Bb2. Engine assessment treats the position as balanced, with 1...c5, 1...Nf6 and 1...e5 preferred.

Several named lines carry a tongue-in-cheek flavor. The Polish Gambit, 1...a5 2. b4, offers the b-pawn and is the mirror image of the Spike Lee Gambit. The Hippopotamus Attack and the Shy Attack are formations in which White advances pawns one square at a time (b3, c3, d3, e3, f3, g3, or g3, d3, e3, h3 with Bg2 and Nd2) while Black builds a classical center with e5, d5, Nf6, Nc6, Bd6 and kingside castling. Minor names include the Andersspike, 1...g6 2. g4, and the Creepy Crawly Formation, 1...e5 2. h3 d5.

The opening is uncommon and often played for psychological reasons, to avoid theory or as a joke, yet online results are evenly split. Anderssen used it again in 1877 and 1878, beating Louis Paulsen, George Henry Mackenzie and James Mason, and Steinitz, Blackburne and Mieses tried it in their era. Croatian IM Zvonko Krečak is a modern adherent. Magnus Carlsen lost with it to Vassily Ivanchuk in a 2010 Amber blindfold game, and Hikaru Nakamura beat Carlsen with it in a 2023 Titled Tuesday event.