The Black Knights' Tango (also known as the Mexican Defense, Two Knights' Tango or Kevitz–Trajkovic Defense) is a chess opening beginning with the moves: 1. d4 Nf6 2. c4 Nc6 This position can also be reached by transposition, for example 1.c4 Nf6, 1.d4 Nc6, or 1.c4 Nc6. History The opening originated in the 1920s, when it was played by both the Mexican grandmaster Carlos Torre (hence the name "Mexican Defense") and the American master Alexander Kevitz (the "Kevitz" in "Kevitz–Trajkovic Defense"). Torre used it to defeat then-U.S. Chess Champion Frank James Marshall in only seven moves. It was later played by the Yugoslav master Mihailo Trajkovic and the Soviet grandmaster Anatoly Lutikov. After decades of obscurity, the opening was revitalized by the International Master Georgi Orlov, who published a booklet and a book about it in 1992 and 1998, respectively. Orlov rechristened the opening the "Black Knights' Tango". Since 1992, the opening has been employed by a number of strong grandmasters, including Victor Bologan, Joel Benjamin, Larry Christiansen, and Alex Yermolinsky. Yermolinsky has even ventured it against Garry Kasparov. Basic ideas Although fairly uncommon, the "Tango" has a sounder positional basis than most other offbeat openings: Black quickly, has a flexible pawn structure, and is prepared to strike back in the center with 3...e5, or with ...e6 and ...d5. The opening has some distinct variations but it is highly transpositional, and may transpose to the King's Indian Defense, Nimzo-Indian Defense, Bogo-Indian Defense, Chigorin Defense, Ragozin System, Catalan Opening, and English Opening. Possible continuations 3.Nf3 The most common move, preventing 3...e5. Black usually responds with 3...e6, although 3...d6, intending a kind of Old Indian Defense, is also possible. After 3...e6, White can play 4.Nc3 Bb4 (transposing to the Nimzo-Indian Defense); 4.a3, when Black can either play 4...d5 (reaching a kind of Queen's Gambit Declined or Ragozin System), or 4...d6 preparing 5...e5 or even 5...g6 ("championed by Bologan", according to Palliser), reaching a sort of King's Indian Defense; or 4.g3, when Black can transpose to the Catalan Opening with 4...d5, recommended by Palliser or 4...Bb4+, preferred by Orlov, which transposes to a Nimzo-Indian after 5.Nc3, or to a Bogo-Indian Defense after 5.Bd2 or 5.Nbd2. 3.Nc3 This is White's second-most popular move. After the thematic 3...e5, one possibility for White is 4.Nf3, transposing to an English Opening. Palliser recommends 4...e4 in response, while Orlov prefers 4...exd4 5.Nxd4 Bb4. Instead, the main line is