[3] Grandmaster John Nunn attributes the Sicilian Defence's popularity to its "combative nature": "in many lines Black is playing not just for equality, but for the advantage.

"The earliest recorded notes on the Sicilian Defence date back to the late 16th century by the Italian chess players Giulio Polerio and Gioachino Greco.

The pawn trade also opens the c-file for Black, who can place a rook or queen on that file to support the queenside counterplay.

In many variations, White castles queenside to exploit attacking chances on the kingside at the cost of moving his king to the flank where Black has a spatial advantage.

[8] It was later the subject of analyses by leading players of the day Alessandro Salvio (1604), Don Pietro Carrera (c. 1617), and Gioachino Greco (1623), and later Conte Carlo Francesco Cozio (c. 1740).

The great French player and theoretician André Danican Philidor opined of the Sicilian in 1777, "This way of opening the game ... is absolutely defensive, and very far from being the best ... but it is a very good one to try the strength of an adversary with whose skill you are unacquainted.

[10] The Sicilian was fairly popular for much of the nineteenth century; Louis-Charles Mahé de La Bourdonnais, Adolf Anderssen, Howard Staunton, Louis Paulsen, and Carl Jaenisch all played it with some consistency.

"[11] Staunton wrote of the Sicilian, "In the opinion of Jaenisch and the German Handbuch, with which I coincide, this is the best possible reply to 1.P-K4, [1.e4 in algebraic notation] 'as it renders the formation of a centre impracticable for White and prevents every attack'.

"[15] George H. D. Gossip, in The Chess Player's Manual, first published in 1874, wrote, "Of late years ... discoveries have been made which have the effect of considerably strengthening White's attack, and the 'Sicilian' is now considered by most modern authorities to be a comparatively weak mode of play.

"[16] Freeborough and Ranken, in their treatise Chess Openings: Ancient and Modern (1889, 1896), wrote that the Sicilian "had at one time the reputation of being the best reply to 1.P-K4 [1. e4], but this has not been confirmed by popular practice.

[19] Similarly, James Mason wrote, "Fairly tried and found wanting, the Sicilian has now scarcely any standing as a first-class defence.

[27] The following year, the authors of Modern Chess Openings (4th edition) wrote, "The Sicilian has claims to be considered as the best of the irregular defences to 1.P-K4 at Black's disposal, and has been practised with satisfactory results by the leading players of the day.

"[C] In this period Black's approach was usually slow and positional, and the all-out attacks by White that became common after World War II had not yet been developed.

Reuben Fine, one of the world's leading players during this time period, wrote of the Sicilian in 1948, "Black gives up control of the centre, neglects his development, and often submits to horribly cramped positions.

"[D] Later, Bent Larsen, Ljubomir Ljubojević, Lev Polugaevsky, Leonid Stein, Mark Taimanov, and Mikhail Tal all made extensive contributions to the theory and practice of the defence.

Both players favoured sharp, aggressive play and employed the Sicilian almost exclusively throughout their careers, burnishing the defence's present reputation.

It produces the psychological and tension factors which denote the best in modern play and gives notice of a fierce fight on the very first move.

This variation leads to extremely sharp play and is ferociously complicated, since the players castle on opposite wings and the game becomes a race between White's kingside attack and Black's queenside counterattack.

Unlike the other major variations considered in this section, Black defers the development of the king's bishop in favour of bringing out the queen's knight.

While theory indicates that Black can hold the balance in the Keres Attack, players today often prefer to avoid it by playing 5...a6 first, an idea popularized by Kasparov.

Top players who have used this variation include Magnus Carlsen, Vladimir Kramnik, Veselin Topalov, Teimour Radjabov, Boris Gelfand, Michael Adams and Alexander Khalifman, among many others.

The move 4...e5 has had a long history; Louis-Charles Mahé de La Bourdonnais used it in his matches against Alexander McDonnell in 1834, and it was also popular for a short time in the 1940s.

These earlier games focused on the Löwenthal Variation (similar to the Kalashnikov but the reply to 5.Nb5 is 5...a6) with 4...e5 5.Nb5 a6 6.Nd6+ Bxd6 7.Qxd6 Qf6, where Black gives up the two bishops to achieve a lead in development.

The ideas in this line are similar to those in the Sveshnikov – Black accepts a backward pawn on d6 and weakens the d5-square but gains time by chasing the knight.

The Kasparov Gambit 8...d5 was played twice in the World Chess Championship 1985, but virtually disappeared from master praxis after the game Karpov–Van der Wiel, Brussels (SWIFT) 1986.

The Pin Variation (also called the Sicilian Counter-Attack) is considered theoretically suspect, but if White is unprepared the tactics can be difficult to calculate at the board.

The Italian American Grandmaster Fabiano Caruana is perhaps the biggest proponent of this line at the top level, and has played this variation in Games 1, 3 and 5 of his World Championship Match against Magnus Carlsen.

With 3.d3, White plans to develop in King's Indian Attack style with g3 and Bg2; this line was used by Fischer to crush Oscar Panno in a famous game (Fischer–Panno, Buenos Aires 1970).

3.c3 will transpose to lines of the Alapin Variation after 3...Nf6, or the French Defence after 3...d5 4.e5 Nc6 5.d4, though 4...d4 is stronger, as after 5.cxd4 cxd4 6.Qa4+ Nc6 7.Bb5 Bd7 8.Bxc6 Bxc6 9.Qxd4 Bxf3 is a strong pawn sacrifice, giving Black excellent compensation.

In 1851, when the Great Exhibition London Tournament was commenced, it was entirely out of favor, but its successful adoption on so many occasions by Anderssen, the first prize winner, entirely restored it to confidence.