Löwenthal Variation

The Löwenthal Variation arises from the Open Sicilian after 2...Nc6 when Black attacks the centralized knight immediately with 4...e5. Black does not hold the e-pawn back for a later decision. The pawn structure is fixed at once, the knight on d4 has to move, and Black gains time and a firm foothold in the center. The concessions are lasting: d5 becomes a hole that White's pieces can occupy, and the d-pawn, once it stands on d6, is backward on a half-open file. In a narrower sense the name refers to the line 5. Nb5 a6, while 5...d6 is known as the Kalashnikov Variation.

The critical retreat is 5. Nb5, which eyes d6 and threatens a knight check there. After 5...a6 the main line runs 6. Nd6+ Bxd6 7. Qxd6 Qf6, with 7...Qe7 as an alternative. Black gives up the bishop pair and in return gains development while White's queen is harassed. The queen most often goes back to d1, though several other squares are tried, and an immediate exchange of queens is uncommon. The Kalashnikov, 5...d6, keeps the dark-squared bishop and covers d6 directly. Evgeny Sveshnikov popularized it in the late 1980s, and it is now considerably more popular than 5...a6.

White has quieter options. 5. Nb3 is played occasionally. 5. Nxc6 is the most frequent reply in the Lichess database, slightly ahead of 5. Nb5, but it releases the central tension, and Black scores marginally better than White after it. White's results improve after 5. Nb5. The engine also ranks 5. Nb5 first, ahead of 5. Nb3 and 5. Nxc6, and it assesses the position after 4...e5 as a slight edge for White. Overall results in the database are almost exactly even.

The line is one of the oldest in the Sicilian. La Bourdonnais played it in his 1834 matches against McDonnell. It takes its name from Johann Löwenthal, one of the leading players of the mid-nineteenth century. It has had periods of popularity since then, notably in the 1940s, but it lost ground once analysis showed that White keeps an advantage in a number of lines.