Karel Opočenský applied the idea against, among others, Gideon Ståhlberg at Poděbrady 1936,[1] Paul Keres at Pärnu 1937,[2] Erich Eliskases at Prague 1937, and Theo van Scheltinga at the Buenos Aires Chess Olympiad 1939.

by B. Argunow written in Kuibyshev (Samara since 1991), Russia, that was published in the second 1946 issue of the magazine Shakhmaty v SSSR.

(Black players leery of the double-fianchetto system, where White plays g3 and b3 and fianchettos both bishops, have preferred 5...g6 intending 6.b3 Bg7 7.Bb2 Nxa6!

The point is that it is awkward for White to meet the threat of ...Nb4, hitting d5 and a2, when Nc3 may often be met by ...Nfxd5 because of the latent pin down the long diagonal.

Another option, popular at the grandmaster level as of 2004 and considered safer for Black, is to accept the pawn with 4.cxb5 but then immediately return it with 4...a6 5.b6.

Such lines include the Poisoned Knight Variation where after 5.Nc3 e6 6.e4 exd5 and 7.e5, Black sacrifices a knight for a large central pawn majority and excellent spatial advantage with good attacking chances; and the River Styx Attack, which continues 5.Nc3 Ba6 6.e4 d6 7.f4 g6 8.e5.

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, Mikhail Tal, and Magnus Carlsen; and grandmasters Vasyl 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.