Benko Gambit


The Benko Gambit is a chess opening characterised by the move 3...b5 in the Benoni Defence arising after:
The Encyclopaedia of Chess Openings has three codes for the Benko Gambit:
The idea of sacrificing a pawn with...b5 and...a6 is quite old. Karel Opočenský applied the idea against, among others, Gideon Ståhlberg at Poděbrady 1936, Paul Keres at Pärnu 1937, Erich Eliskases at Prague 1937, and Theo van Scheltinga at the Buenos Aires Chess Olympiad 1939. Later the Mark Taimanov versus David Bronstein game at the Candidates Tournament, Zürich 1953, drew attention. Most of these games began as a King's Indian, with Black only later playing...c5 and...b5. Possibly the first to use the now-standard move order 1.d4 Nf6 2.c4 c5 3.d5 b5 was Thorvaldsson–Vaitonis, Munich Olympiad 1936.
In many countries, particularly in the Eastern Bloc, the opening is known as the Volga Gambit. This name is derived from the Volga River after an article about 3...b5 by B. Argunow written in Kuibyshev, Russia, that was published in the second 1946 issue of the magazine Shakhmaty v SSSR.
Beginning in the late 1960s, this opening idea was also promoted by Hungarian-American grandmaster Pal Benko, who provided many new suggestions and published his book The Benko Gambit in 1974. The name Benko Gambit stuck and is particularly used in English-speaking countries.
In his 1974 book, Benko drew a distinction between the Benko Gambit and the Volga Gambit: "Volga Gambit" referred to the move 3...b5, while the "Benko Gambit" consisted of the moves 3...b5 4.cxb5 a6, which is now considered the main line. Now the terms are synonyms and are used interchangeably or joined together with a hyphen.

Theory

The main line continues with the moves 4. cxb5 a6 5. bxa6 Bxa6 followed by Black fianchettoing the f8-bishop. Black's compensation for the pawn takes several forms. First, White, who is already behind in, must solve the problem of developing the f1-bishop. After 6. Nc3 d6, if White plays 7. e4, then Black will play 7...Bxf1, and after recapturing with the king, White will have to spend time castling artificially with g3 and Kg2, as in the line 7...Bxf1 8. Kxf1 g6 9. g3 Bg7 10. Kg2. If White avoids this by fianchettoing the bishop, it will be in a rather passive position, being blocked by White's own pawn on d5.
Apart from this, Black also obtains fast development and good control of the a1–h8 diagonal and can exert pressure down the half-open a- and b-files. These are benefits which can last well into the endgame and so, unusually for a gambit, Black does not generally mind if queens are exchanged; indeed, exchanging queens can often remove the sting from a attack by White.
Although the main line of the Benko is considered acceptable for White, there are various alternatives that avoid some of the problems entailed in the main line. The simplest is to just decline the gambit with 4.Nf3. Other possible moves are 4. Nd2, 4. a4, 4. e3 and 4. Qc2. Another idea, popular at the grandmaster level as of 2004, is to accept the pawn but then immediately return it with 4. cxb5 a6 5. b6.

Sosonko Variation

After 4. a4 by white, black has three sound replies. The most popular line is the Sosonko Accepted variation, where 4. bxc4 is played by black. This can, and frequently does, lead to very sharp and sacrificial variations for both sides. Such lines include the poisoned knight variation where after 4. a4 bxc4, 5. Nc3 e6, 6. e4 exd5 and 7. e5, black sacrifices a knight for a huge central pawn majority, an excellent spacial advantage with good attacking chances, and the River Styx Attack, where 5. Nc3 Ba6, 6. e4 Nf6, 7. f4 d6, 8. Nf3 g6, 9. e5 is played. This leads to a very sharp, and extremely complicated pawn sacrifice by white, where white often delays or even stops black castling either side, has a solid grip over the kingside with the pawn e6 and Nf7 outpost combo. It is named after the Greek Mythological river that interconnects the Earth and the Underworld.
These lines are incredibly diverse and complicated; they require much more exploration. Players who wish to avoid the fully accepted, and usually play the pawn return variation, ought to consider this variation for play as well.
Other less common lines include the Advance variation with 4. a4 b4, leading to very positional games with pseudo-benoni structures, and the rare 4. Qa5+ which often transposes into an altered advance variation with white playing 5. Bd2 to block the check, and black responding with 5. b4.

Use

The gambit's most notable practitioner was its eponym, Pal Benko. Many of the world's strongest players have used it at one time or another, including former world champions Viswanathan Anand, Garry Kasparov, Veselin Topalov, and Mikhail Tal; and grandmasters Vassily Ivanchuk, Michael Adams, Alexei Shirov, Boris Gelfand, and Evgeny Bareev. It is a popular opening at amateur level, where it is considered to offer Black good practical chances of playing for a win.