Sicilian Defence (Alapin Variation)

This is one of the main "anti-Sicilians", a way for White to avoid the theory-dense open lines following 2. Nf3.

2. c3 supports pushing the pawn to d4. If 2...Nc6!?, which is a common amateur try, 3. d4 cxd4 4. cxd4 and White has achieved a two-pawn centre. When they played 1...c5, Black had hoped for an edge by taking central pawn with a less-important flanking c-pawn, but this disappeared when White was able to recapture with their own flank pawn. The line continues 4...d5 5. exd5 (5. e5?! allows Black to play ...Bf5 and ...e6, for an improved French defence structure) Qxd5 6. Nf3 e5 7. Nc3 Bb4 8. Bd2 Bxc3 9. Bxc3 e4 10. Ne5 Nxe5 11. dxe5 Ne7⩲

However, 2. c3 has the drawback of taking away the c3 square which White would otherwise like to place their knight. Black's two main moves, 2...d5 and 2...Nf6, seek to take advantage of this.

2...d5 threatens 3...dxe4, and after 3. exd5 Qxd5, the Barmen defence, White can still play 4. d4, but they no longer get two pawns in the centre and Black has a development lead. White is unable to play Nc3 with tempo on the queen because they have already occupied that square with a pawn, and Black is in no hurry to play ...cxd4 cxd4 and free the c3 square for White. 2...d5 is the old main line.

2...Nf6 has gained popularity and is now main response. 2...Nf6 attacks the pawn on e4, and White cannot defend with Nc3. The main line is 3. e5 Nd5 (3...Ne4? 4. d3! traps the knight) 4. d4 (threatening 5. c4 & 6. d5) cxd4, transposing into a Smith-Morra gambit declined. 5. cxd4 (or 5. Nf3 Nc6 6. cxd4) is usually met with ...d6, preparing to chip away at the pawn chain, or ...e6. Although not as aggressive for Black, it allows for a more solid structure going into the middle game.

2...d6?! is occasionally played, where Black just allows White to take the full centre, as is 2...e6!? with the idea of 3...d5 and potentially transposing into a French defence, advance variation.

The earliest recorded game in this opening is Wolf Popert versus Howard Staunton, 1841.^[1] Staunton played 2...e6 and the game transposed into an advance French. It is named after Semyon Alapin, who played it first in Vienna in 1898.^[2][3][4]

One of its leading adherents in the 20th century was Evgeny Sveshnikov, who remarked that "I can confidently say that the move 2. c3 has fed me and my family for almost forty years."^[5]

Deep Blue employed the Alapin against Kasparov in games 1 and 3 of their 1996 match.^[6][7]

Today it is a popular anti-Sicilian employed at the highest levels, including by Magnus Carlsen.^[8] A similar line is to play c3 on the third move, after 3. Nf3. By delaying c3, Black faces different choices depending on how they moved, e.g. 2. Nf3 d6 3. c3 and were Black to play ...d5, as they might against 2. c3, they have lost a tempo.

1. e4 c5 2. c3

• The Alapin (c3) ⎸Sicilian Defense Theory - HangingPawns (YouTube)

Wikipedia has related information at Sicilian Defence, Alapin Variation.